DMG 24. Guide to World War II Hangars. 03 - Type C Hnagarswebarchive.nationalarchives.gov.uk/20121026065214/ · Guide to World War II Hangars 03 - Type C Hangars December 2001 v Abbreviations

DEFENCE ESTATESDEFENCE ESTATESDEFENCE ESTATESDEFENCE ESTATESMINISTRY OF DEFENCEMINISTRY OF DEFENCEMINISTRY OF DEFENCEMINISTRY OF DEFENCEWIND SENSITIVE STRUCTURESWIND SENSITIVE STRUCTURESWIND SENSITIVE STRUCTURESWIND SENSITIVE STRUCTURES

December 2001

Design and Maintenance Guide 24Design and Maintenance Guide 24Design and Maintenance Guide 24Design and Maintenance Guide 24

Guide to World War IIHangars03 - Type C Hangars

Guide to World War II Hangars03 - Type C Hangars

December 2001

Crown Copyright 2001Published by the Ministry of Defence


December 2001 iiii

Foreword

This Guide was prepared under the patronage of HQ STC.

This document is for the use of Top Level Budget Holders (TLBHs) for application bythe Project Sponsors, Property Managers (PROMs), Establishment Works Consultants(EWCs), Works Services Managers (WSMs) and other parties connected with the hangar.For Projects, the principal users of the document are expected to be Project Sponsors toinfluence the preparation of the Statement of Requirements, the Project Manager and thedesigners and installers. In addition, for works services falling within the PropertyManagement remit, the EWC assists the Property Manager in determining the descriptionof task and the WSM is responsible for design, installation and maintenance.

MOD addressees should ensure that designers and contractors employed for worksconnected with the Type C hangar are advised of this Guide.

Amendments to this Guide will be advised by Defence Estates (DE) Technical Bulletin,issued to PROM and TLBH Works staff. It is the responsibility of the user to check withthe PROM or Project Sponsor if amendments have been issued. There is a feedback format Annex B, for suggested changes or developments to the document.

A hangar notification form is also included at Annex C for feedback on any hangar relatedproblems or works on a hangar building.

Technical advice and assistance can be obtained from DE. Approaches may be throughlocal DE offices or directly to the Focal Point:

Wind Sensitive StructuresSpecialist ServicesDefence EstatesBlakemore DriveSutton ColdfieldWest Midlands B75 7RL

All enquiries in connection with drawings and requests for copies of drawings should beaddressed to:

Library (DE Information Management)Defence EstatesBlakemore DriveSutton ColdfieldWest Midlands B75 7RL

Information provided is for guidance only and it must be verified and checked for eachindividual project or works service.


Foreword

December 2001iiiiiiii

Use of this Guide does not absolve a Project Manager or WSM from any responsibilityrelating to the design, neither does the existence of the Guide constrain the ProjectManager or WSM from using alternatives, provided such alternatives can bedemonstrated to provide a result of equal safety, quality and cost effectiveness.

This Guide has been devised for the use of the Crown and its Contractors in theexecution of contracts for the Crown. The Crown hereby excludes all liability(other than the liability for death or personal injury) whatsoever and howsoeverarising (including, but without limitation, negligence on the part of the Crown, itsservants or agents) for any loss or damage however caused where the Guide is usedfor any other purpose.

Compliance with a DE Design and Maintenance Guide will not of itself confer immunityfrom legal obligations.


December 2001 iiiiiiiiiiii

Acknowledgement


December 2001iviviviv

Amendments

Amendments Page No Date Inserted By


December 2001 vvvv

Abbreviations

BS British Standard

DCI Defence Council Institution

DE Defence Estates

DMG DE Design & Maintenance Guide

DWS Defence Works Services

EWC Establishment Works Consultants

HQ STC Headquarters Strike Command

JSP Joint Services Publication

MHE Mechanical Handling Equipment

MOD Ministry of Defence

PM Project Manager

PROM Property Manager

TB DE Technical Bulletin

WSM Works Services Manager


December 2001vivivivi


December 2001 viiviiviivii

Contents

FOREWORDFOREWORDFOREWORDFOREWORD

ACKNOWLEDGEMENTACKNOWLEDGEMENTACKNOWLEDGEMENTACKNOWLEDGEMENT

ABBREVIATIONSABBREVIATIONSABBREVIATIONSABBREVIATIONS

1.1.1.1. INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTION

2.2.2.2. BACKGROUNDBACKGROUNDBACKGROUNDBACKGROUND

2.1 HISTORY OF TYPE-C HANGARS2.2 USAGES TODAY2.3 LOCATIONS OF EXISTING TYPE-C HANGARS

3.3.3.3. DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION

3.1 IDENTIFICATION3.2 DRAWINGS3.3 MAIN STRUCTURAL ARRANGEMENTS

4.4.4.4. STRUCTURAL APPRAISALSTRUCTURAL APPRAISALSTRUCTURAL APPRAISALSTRUCTURAL APPRAISAL

4.1 DESIGN PHILOSPHY4.2 MEMBERS ANALYSED4.3 BACKGROUND TO PERMISSIBLE STRESSES AND LOADING

USED IN THE APPRAISAL4.4 OUTCOME4.5 CONCLUSION4.6 IMPLICATIONS OF APPRAISAL CONCLUSION

5.5.5.5. OPERATIONAL REQUIREMENTSOPERATIONAL REQUIREMENTSOPERATIONAL REQUIREMENTSOPERATIONAL REQUIREMENTS

5.1 INTRODUCTION5.2 HANGAR BUILDING5.3 PROFESSIONAL AND TECHNICAL INSPECTIONS

6.6.6.6. REFURBISHMENT – GENERALREFURBISHMENT – GENERALREFURBISHMENT – GENERALREFURBISHMENT – GENERAL

6.1 INTRODUCTION6.2 OPTIONS AND RECOMMENDATIONS6.3 WARRANTIES/GUARANTEES

7.7.7.7. REFURBISHMENT – ROOFINGREFURBISHMENT – ROOFINGREFURBISHMENT – ROOFINGREFURBISHMENT – ROOFING

7.1 DESCRIPTION7.2 PROBLEMS7.3 ROOFING REQUIREMENTS7.4 ROOFING MATERIAL7.5 ROOFING OPTIONS7.6 DETAILED DESCRIPTION OF ROOFING OPTIONS7.7 SUMMARY OF ROOFING OPTIONS


December 2001viiiviiiviiiviii

8.8.8.8. REFURBISHMENT - GUTTERS AND DRAINAGEREFURBISHMENT - GUTTERS AND DRAINAGEREFURBISHMENT - GUTTERS AND DRAINAGEREFURBISHMENT - GUTTERS AND DRAINAGE

8.1 DESCRIPTION8.2 PROBLEMS8.3 GUTTER PROPOSALS8.4 GUTTER MATERIAL OPTIONS8.5 GUTTER ARRANGEMENT8.6 SNOWBOARDS8.7 BELOW-GROUND DRAINAGE

9.9.9.9. REFURBISHMENT – WINDOWSREFURBISHMENT – WINDOWSREFURBISHMENT – WINDOWSREFURBISHMENT – WINDOWS

9.1 DESCRIPTION9.2 PROBLEMS9.3 PROPOSAL FOR WINDOWS

10.10.10.10. REFURBISHMENT – WALLSREFURBISHMENT – WALLSREFURBISHMENT – WALLSREFURBISHMENT – WALLS

10.1 DESCRIPTION10.2 REINFORCED CONCRETE10.3 DETERIORATION OF WALLS10.4 ALTERATIONS10.5 TREATMENT OF EXISTING CLADDING10.6 PROPOSALS FOR SOLID WALLS

11.11.11.11. REFURBISHMENT – DOORSREFURBISHMENT – DOORSREFURBISHMENT – DOORSREFURBISHMENT – DOORS

11.1 DESCRIPTION11.2 PROBLEMS11.3 DOOR OPTIONS11.4 DOOR INSPECTIONS11.5 HANGAR DOOR OUTRIGGERS11.6 BLAST AND FRAGMENT PROTECTION

12.12.12.12. ROOF ACCESSROOF ACCESSROOF ACCESSROOF ACCESS

13.13.13.13. STANDARD AND REGULATIONSSTANDARD AND REGULATIONSSTANDARD AND REGULATIONSSTANDARD AND REGULATIONS

13.1 BUILDING REGULATIONS13.2 PLANNING AND FIRE OFFICER APPROVALS13.3 CROWN FIRE STANDARDS13.4 HEALTH AND SAFETY13.5 PHYSICAL SECURITY13.6 ENVIRONMENTAL LEGISLATION

ANNEXESANNEXESANNEXESANNEXES

A RECORD DRAWINGSB CHANGE SUGGESTION FORMC HANGAR NOTIFICATION FORMD BASIC WIND SPEED MAPE SAFE LOADINGF ROOFING OPTIONS & DESCRIPTION OF ROOFING MATERIALSG WINDOW REFURBISHMENT OPTIONS & TYPICAL WINDOW DRAWINGSH DOOR REFURBISHMENT OPTIONSI COST COMPARISONS

REFERENCESREFERENCESREFERENCESREFERENCES

Guide To World War II Hangars03 - Type C Hangars

December 2001 1111

1 Introduction

SCOPESCOPESCOPESCOPE

The content of this Guide is applicable to works services and projects. Itincludes new build, maintenance and refurbishment work. In addition, theguidance relates to safe usage of the hangar and the operations within thestructure and in its vicinity.

This Guide is intended for use by:

• Property Managers (PROMs), Establishment Works Consultants (EWCs) andWorks Services Managers (WSMs)

• Project Sponsors, Project Managers, design consultants and contractors• users of a Type-C hangar and those engaged in duties connected with the hangar.

MOD addressees should ensure that designers and contractorsemployed for works connected with the Type C hangar are advised of thisGuide.

This Guide is to be used to provide preliminary advice to assist in thepreparation of Statements of Requirement, the undertaking of Option Studiesand the preparation of Technical Briefs. It may also be used as the basis for ProfessionalAppraisals as required by DE Specification 005. However, all works be they majorrepair, major refurbishment or demolition must be supported by an adequate site surveyand appropriate assessments by competent engineers.

SUMMARY OF CONTENTSUMMARY OF CONTENTSUMMARY OF CONTENTSUMMARY OF CONTENT

A description is given of the typical Type C hangar, how it can be identified, itstypical structural form and features, drawings that have been prepared for a typical TypeC hangar. Using archive drawings as a basis, CAD drawings have been prepared by DEto record the key features of a Type C hangar.

A structural appraisal of the hangar has been carried out. This indicates that, generally,the hangars are adequate to cover current loadings providedmoderate precautions are taken. Hangars in more exposed locations must be consideredindividually.

Precautions must be taken for the safe undertaking of activities and operationswithin the hangar and in its vicinity. For example, heavy snowfall can applyexcessive loading, due to snow infilling the valleys of the multi-pitched roof.In addition, high winds can necessitate closure of the hangar doors to reduce theeffect of dominant openings. The safe use of doors is also addressed with regardto their operation, inspection and maintenance.


1 Introduction

December 20012222

The Guide covers hangar refurbishment and the common work items with whicha PROM or Project Sponsor will become involved, eg. re-roofing, wall claddingand repair or renewal of doors and windows. Guidance is given in respect ofMOD policy, working practices and other standards or codes. Typical solutionsare given with illustrations for re-roofing and recladding the walls.

Refurbishment options have been developed to include whole life costs.Therefore, the initial costs of the appropriate roofing or cladding solution havebeen considered in conjunction with subsequent maintenance and operationalcosts eg. those due to heating losses.

The implications of applying the requirements of Crown Fire Standards areaddressed where appropriate. MOD security matters are also discussed in the document.

This Guide explains how the Type C structure was appraised, the designphilosophy adopted and findings of the analysis. Historical design codes,steelwork stresses and the loading criteria are covered. With regard to windloading, the significance of dominant openings in a hangar building due to doorsand windows and the building's permeability is also explained.

In summary, it is usually feasible to refurbish a Type-C hangar with practical,economical and attractive, economical solutions, rather than demolish andrebuild. Each hangar should be assessed on a site specific basis, because severalfactors influence a decision. These include local variations in snow and windloading, local labour and materials costs, local planning restrictions for useof the building and the proposed life of the hangar.

The Type C hangar with its open area of some 4180m² (45,000 sq ft) and a clearheadroom for 1934 hangar of 10.770m (35'-4"), and for 1938 hangar of 9.246m (30'-4"),provides a functional and flexible working facility. With adequate routine maintenanceand the careful consideration of major refurbishment options, particularly re-roofing,Type C hangars should continue to offer economic hangar accommodation for manyyears.

Readers are reminded of the general duty to provide information on hangar relatedproblems and hangar projects. A proforma is attached at Annex C. The informationobtained from this process enables DE to disseminate relevant hangar related technicalguidance.


December 2001 3333

2 Background

2.1 HISTORY OF TYPE-C HANGARS HISTORY OF TYPE-C HANGARS HISTORY OF TYPE-C HANGARS HISTORY OF TYPE-C HANGARS

The Type-C hangar is the most common of all MOD wartime hangars. In theorder of 200 Type-C hangars are still in use on the MOD estate in the UK. Withgood maintenance and periodic refurbishment, many more years of service can beprovided.

The first Type-C hangars were constructed in the interwar RAF expansion period ofthe mid-1930's. The design evolved from the earlier type A and B hangarsdeveloped during the 1920's. Their construction continued until the early 1940'swhen, due to wartime commitments, the RAF needed hangars which could be builtmuch faster, and so other types of hangar, mainly of a lighter construction,superseded the Type-C.

2.2 USAGES TODAY USAGES TODAY USAGES TODAY USAGES TODAY

The predominant use today is still as aircraft accommodation. Many old airfieldshave now passed from the RAF to the Army, and the hangars continue to be used forother purposes such as motor transport, garaging and workshops, and the storage ofequipment and materials.

2.3 LOCATIONS OF EXISTING TYPE-C HANGARS LOCATIONS OF EXISTING TYPE-C HANGARS LOCATIONS OF EXISTING TYPE-C HANGARS LOCATIONS OF EXISTING TYPE-C HANGARS

The list overleaf illustrates known locations of Type-C hangars on the MOD estate.It is believed, however, that the list is not complete and there are Type-C hangars atother locations. Some hangars listed may have been disposed of, either bydemolition or through sale. However, the list is the best available at this time and isgiven for information purposes only.

Establishments with Type C Hangar which are not included are requested tocomplete the form at Annex C and return to the Wind Sensitive Structures Section,Specialist Services at Sutton Coldfield.


2 Background

December 20014444

Locations of existing Type-C hangarsLocations of existing Type-C hangarsLocations of existing Type-C hangarsLocations of existing Type-C hangars

1 Abingdon, Dalton Barracks (1) 35 Locking, RAF (1)2 Aldergrove, RAF (4)) 36 Lossiemouth, RAF (3)3 Aston Down, PESD (1) 37 Manby (5)4 Bassingbourn, Army (4)0 38 Marham, RAF (5)5 Benson, RAF (4) 39 Middle Wallop, AAC (5)6 Bicester, RAF (1) 40 Mildenhall, RAF (2)7 Binbrook, RAF (5) 41 Molesworth, RAF (1)8 Boscombe Down, DERA (1) 42 Netheravon Airfield (1)9 Bramcote, RAF (5) 43 Newton, RAF (5)10 Brize Norton, RAF (4) 44 Northolt, RAF (1)11 Catterick, Army (2) 45 Odiham, RAF (3)12 Church Fenton, RAF (2) 46 Scampton, RAF (4)13 Coltishall, RAF (4) 47 Sealand, RAF (1)14 Cosford, RAF (3) 48 Shawbury, RAF (4)15 Cottesmore, RAF (4) 49 South Cerney, Army (2)16 Cranwell RAF (2) 50 St Athan, RAF (4)17 Debden, RAF (1) 51 St Eval, RAF (1)18 Dishforth, Army & RAF (5) 52 Stradishall, RAF (1)19 Driffield, Alamein Barracks (4) 53 Ternhill, Clive Barracks (1)20 Feltwell, RAF (5) 54 Thorney Island, Baker Barracks (1)21 Finningley, RAF (5) 55 Topcliffe, Army & RAF (5)22 Gosport, HMS Sultan (1) 56 Turnhouse, RAF (1)23 Hemswell (4) 57 Upavon, Army (2)24 Honington, RAF (5) 58 Upwood, RAF (2)25 Hullavington, Army (4) 59 Waddington, RAF (2)26 Kemble, RAF (2) 60 Wattisham Airfield, Army (4)27 Kinloss, RAF (3) 61 Watton, RAF (4)28 Kirton Lindsey, Army (3) 62 West Raynham, RAF (4)29 Leconfield, ASMT (5) 63 Wick, RAF (1)30 Leeming, RAF (5) 64 Wittering, RAF (2)31 Leuchars, RAF (4) 65 Wroughton, RAF (1)32 Lindholme, RAF (1) 66 Wyton, RAF (4)33 Linton-on-Ouse, RAF (5)34 Little Rissington (4)

(Total: approximately 196Type-C hangars remaining at 66 establishments)


December 2001 5555

3 Description

3.1 IDENTIFICATION IDENTIFICATION IDENTIFICATION IDENTIFICATION

3.1.1 General General General General

Before commencing work on any hangar, it is clearly important to correctlyidentify the hangar type. The Type-C hangar is rarely confused with other types,exhibiting a typical multi-pitch roof with a series of ridges and valleys. The onlyother similar hangars are the Type-A and Type-B from which the Type-C designevolved, and few of these earlier types still remain.

Virtually all Type C hangar roofs have the same steel structural frame, comprising aseries of primary trusses at 7.62m centres (25ft) each with a clear span of 45.72m(150ft). The primary trusses, in turn, support secondary trusses at 4.572m centres(15ft). This structure forms the multi-pitched roof arrangement with a primary trussaligned on each ridge. At each end of the hangar there are six full height slidingdoors, allowing both ends to be fully opened up.

3.1.2 Variations Variations Variations Variations

The Type-C hangar may vary in length, internal headroom and cladding material.The overall length is typically 91.44m and varies in 7.62m (25ft) increments from45.72m to 91.44m (150ft to 300ft). The internal clear height for 1934 hangar of10.770m (35'-4"), and for 1938 hangar of 9.246m (30'-4"), with an original roofcovering either of asbestos cement slates or sheeting. The side walls are usually ofbrick or concrete although in the Cotswold area, they are sometimes in stone. Thefollowing table illustrates the main variations of Type-C hangars:


3 Description

December 20016666

YEARYEARYEARYEAR SUB-SUB-SUB-SUB-GROUPGROUPGROUPGROUP

INTERNALINTERNALINTERNALINTERNALWidth x HeightWidth x HeightWidth x HeightWidth x Height

DIMENSIONSDIMENSIONSDIMENSIONSDIMENSIONSLengthLengthLengthLength

WALLSWALLSWALLSWALLS DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION

1934 (1)

(2)

45.72m x 10.770m

45.72m x 10.770m

45.72m x 10.770m

91.44m

45.72m to 91.44m

45.72m to 91.44m

Brick or stone

Brick or stone

Concrete

Hipped end to each duo-pitch roof bay. Hangar 12 bays longand hangar gable ends align with a ridge. One patent glazedwindow to each bay, approx 6.2m wide x 4.4m high. Solidwall construction to top of wall at roof parapet level.

Hipped end to each duo-pitch roof bay. Hangar lengthdetermined by whole number of 7.62m bays. Hangar gable endalign with a ridge, providing a vertical face of cladding abovethe doors. Windows and walls as before.

Ditto1938 45.72m x 9.246m 91.44m Concrete or

brickHipped end to each duo-pitch roof bay. Hangar 11 bays longplus 2no half bays at each end. Ends of hangar provide apitched cantilever roof above the doors. Window heightreduced to 3m but in panels either 13.4m or 21.4m longacross 2 or 3 structural bays. Wall height only to top ofwindows, with asbestos cement cladding above to roof level.

Figure 3.1 Main Variations of Type-C hangars.

The previous table illustrates that there are two main variations of the Type-Changar, the 1934 and the 1938. There is, in addition, a shorter span version, thestructural details of which are not covered by this Guide.

The photographs at figures 3.4 to 3.6 illustrate the typical external appearance of theType C hangar, and show the differences between the 1934 and the 1938 versions.Figure 3.4 shows the rare situation of a 1934 and a 1938 version sited alongsideeach other. Figures 3.5 and 3.6 show enlarged views of these same hangars. Bothhave concrete walls, but each has been overclad during past refurbishment. Thewindow areas have also been overclad in translucent sheeting of the same profile asthe main wall cladding.

3.1.3 Annexes Annexes Annexes Annexes

Most hangars were built with single storey annexes, often to both sides of the hangarand either in brick or concrete according to the hangar wall construction. Theseprovided accommodation for offices, changing rooms, crew rooms, storage andworkshops.

3.2 DRAWINGS DRAWINGS DRAWINGS DRAWINGS

3.2.1 Archive drawings Archive drawings Archive drawings Archive drawings

A full list of microfilmed drawings and paper drawings is listed in Annex A, and areavailable from DE Information Management. These drawings have also beenscanned, and are available in digital format (PDF documents) and are available fromDE Information Management.

Site specific as-built drawings are not kept at DE Information Managementhowever, they may be available from the Property Manager or Project Sponsor for aparticular site.

In view of the reproduction quality of extant drawings, various new drawings wereprepared for each of the 1934 and 1938 versions (sect 3.2.2).

The following drawings were used in the structural appraisal and these drawings areavailable from DE Information Management if required.


3 Description

December 2001 7777

HANGARHANGARHANGARHANGARVERSIONVERSIONVERSIONVERSION

DRAWINGDRAWINGDRAWINGDRAWINGNUMBERNUMBERNUMBERNUMBER

DRAWING TITLEDRAWING TITLEDRAWING TITLEDRAWING TITLE STORAGESTORAGESTORAGESTORAGEMEDIUMMEDIUMMEDIUMMEDIUM

1934 2029/34

861/35

865/35

General Arrangement: Plan sections ofsteelwork

Roof Trusses

Roof Trusses

Print

Negative

Negative

Figure 3.2 Archive drawings used in structural appraisal

3.2.2 New DE drawings New DE drawings New DE drawings New DE drawings

The new drawings prepared by redrawing typical original plans and details are listedin the following table:

HANGAR VERSIONHANGAR VERSIONHANGAR VERSIONHANGAR VERSION DRAWING NUMBERDRAWING NUMBERDRAWING NUMBERDRAWING NUMBER DRAWING TITLEDRAWING TITLEDRAWING TITLEDRAWING TITLEC type hangar(1934)

DE/H1/001/101DE/H1/001/102DE/H1/001/103DE/H1/001/104DE/H1/001/105DE/H1/001/106

General Arrangement showing original DrainageFoundation Plan and Details of Door Rail FoundationsGeneral Arrangement: Plan and ElevationsGeneral Arrangement showing Steelwork layoutLine diagram showing layout and member sizes of Girder Truss ‘A’Secondary Truss sizes and layout of members

C type hangar(1938)

DE/H1/001/201DE/H1/001/202DE/H1/001/203DE/H1/001/204DE/H1/001/205DE/H1/001/206

General Arrangement showing original DrainageFoundation Plan and Details of Door Rail FoundationsGeneral Arrangement: Plan and ElevationsGeneral Arrangement showing Steelwork layoutLine diagram showing layout and member sizes of Girder Truss ‘A’Secondary Truss sizes and layout of members

Figure 3.3 Schedule of new DE drawings

The above drawings have been prepared in AutoCAD and are held both on disc andas A1 size prints obtainable from DE Information Management. Copies of thesedrawings reduced to A3 size are included at Annex A.

3.2.3 Use of drawings Use of drawings Use of drawings Use of drawings

Both the archive and newly prepared drawings should only be regarded as indicativeof typical Type-C hangars. For any particular hangar, an on-site inspection shouldbe undertaken to check the as-built structure and building fabric for comparison withthe typical construction. The original as-built drawings for the site should berequested from the Property Manager.


3 Description

December 20018888


3 Description

December 2001 9999

Figure Figure Figure Figure 3.4 3.4 3.4 3.4 View of 1934 and 1938 Versions adjacent each other

Figure Figure Figure Figure 3.5 3.5 3.5 3.5 Typical 1934 Type C Hangar

Figure Figure Figure Figure 3.6 3.6 3.6 3.6 Typical 1938 Type C Hangar


3 Description

December 200110101010


3 Description

December 2001

3.3 MAIN STRUCTURAL ARRANGEMENTS MAIN STRUCTURAL ARRANGEMENTS MAIN STRUCTURAL ARRANGEMENTS MAIN STRUCTURAL ARRANGEMENTS

Figure 3.1 indicated the main variations of Type C hangars. The following sectionsgive further details of the typical main structural arrangements and member sizes.Reference should be made to relevant new drawings in Sect 3.2.2 and to otherarchive drawings for further details. Providing the member sizes and arrangementsare representative of those detailed on the drawings referred to at Section 3.2.2, theappraisal findings in the later sections are appropriate for use at option study stage.

3.3.1 Lattice roof girders Lattice roof girders Lattice roof girders Lattice roof girders

The main girders span the full 45.72m span (150 feet) across the hangar between thecolumns at 7.62 m centres (25 feet) and support the secondary trusses.

For both the Type C34 and Type C38 hangars there are typically three separate maingirders referred to on original drawings as Girders A,D and E and their typicallocations are shown in DE drawings DE/H/001/104 and 204. The three girder typesare similar in size and layout, but by utilising different member sizes have differentcapacities.

Figure 3.7 indicates the typical arrangement and member sizes for Girder A.

C

F

D

C

J

D

FEK

G

A

D

KH

A (plated)

B

KH

B

CCA

H HK

B B D D D

FJF

KG

KKE

LacedColumn

¢

's's

's's

C's

'ss

A (plated) A (plated)A (plated)

46456

LacedColumn

¢

Figure Figure Figure Figure 3.7 3.7 3.7 3.7 M

A 2 / 9" x 31/2" x 22.27 lb/ft BSC B 2 / 9" x 31/2" x 22.27 lb/ft BSC C 2 / 9" x 3" x 17.46 lb/ft BSC D 2 / 9" x 3" x 17.46 lb/ft BSC E 2 / 15" x 6" x 45 lb/ft BSB's F 6" x 5" x 25 lb/ft BSB G 2 / 6" x 31/2" x 16.48 lb/ft BS H 6" x 3" x 12.41 lb/ft BSC J 2 / 6" x 31/2" x 16.48 lb/ft BSCK 2 / 6" x 3" x 12.41 lb/ft BSC'

A 2 / 9” x 3½ x 22.27 lb/ft BSC’sB 2 / 9” x 3½ x 22.27 lb/ft BSC’sC 2 / 9” x 3” x 17.46 lb/ft BSC’sD 2 / 9” x 3” x 17.46 lb/ft BSC’sE 2 / 15” x 6” x 45 lb/ft BSB’sF 6” x 5” x 25 lb/ft BSBG 6” x 3½ x 16.46 lb/ft BSC’sH 6” x 3” x 12.41 lb/ft BSCJ 2/6” x 3½ x 16.48 lb/ft BSC’sK 2/6” x 3” x 12.41 lb/ft BSC’s

11111111

ain Truss Details Girders ‘A’


3 Description

December 200112121212

3.3.2 Secondary trusses Secondary trusses Secondary trusses Secondary trusses

The secondary trusses span 7.62m (25 feet) between the supporting primary trusses.The truss depth varies along its span, having the depth of 4.9m at the supports and1.23m at mid-span, thus forming valley gutters. The original roof was supporteddirectly on the secondary trusses via timber sarking and purlins.

Figure 3.8 illustrates the typical arrangement of a secondary truss with runway beamwhere fitted.

A

AB

C

C

D

FE

A

A

DB

C

EC

M a inT r u s s

¢

M a inT r u s s

¢

M a in t r u s sto p c h o r d

M a in t r u s sb o t to m c h o r d

o r 1 0 " x 6 " A 2 / 4 " x 21 / 2 " x 1 /4 " B 2 / 31 / 2 " x 3 " x 1 /4 " C 2 / 4 " x 3 " x5 /1 6 " D 3 " x 3 " x 1 / 4 " E 2 / 3 " x 3 " x5 / 1 6 " F 2 / 2 " x 21 / 2 " x 1 /4 "

1 0 " x 41 / 2 "R u n w a y B e a m

7 6 2 0

Figure Figure Figure Figure 3.83.83.83.8 Secondary Truss Details

New drawings DE/HI/001/106 and D/DE/HI/001/206 indicate the typicalvariations to secondary roof trusses.


3 Description

December 2001 13131313

3.3.3 Columns and base Columns and base Columns and base Columns and base

A typical supporting column for a Type C hangar comprises two I beams tiedtogether by a system of diagonal lacing angles, and encased in concrete over theirfull height. Fig 3.9 illustrates the concrete foundation detail.

la c e d c o lu m n .

f lo o r le v e l

1 5 2 4 1 5 2 4

762

914

150

Fig Fig Fig Fig 3.93.93.93.9 Column Foundation Detail

C34 columns are restrained at mid height by longitudinal 12” x 4” x 31 lb/ft and 9”x 3” x 17 lb/ft rolled steel channels which run along the length of the hangar.

In each end bay of a Type C38 hangar a horizontal 6” x 3” rolled steel joist tie isprovided.

3.3.4 Runway beams Runway beams Runway beams Runway beams

Two sizes of runway beams traverse the full width of the hangar. These run parallelto the main trusses and are attached to the underside of the secondary trusses at4.572m centres.

i.e. 2no. 10” x 41/2” x 25 lb/ft Joists with 1.5 Tonnes SWL2no. 10” x 6” x 40 lb/ft Joists, with 6 Tonnes SWL

Runway beams are not always present in hangars, neither are they present in eachhangar bay.

3.3.5 Vertical bracing Vertical bracing Vertical bracing Vertical bracing

There are four sets of diagonal vertical bracing, two on each side of the hangar witheach placed in the same structural bay as the roof wind girders at each end of thehangar.

The drawings at sect 3.2.2 indicate the roof wind girder and vertical bracingarrangements.


3 Description

December 200114141414

3.3.6 Roof wind girders Roof wind girders Roof wind girders Roof wind girders

Two lateral wind girders span horizontally across the width of the hangar and arelocated in the last full structural bay at each end of the hangar.

3.3.7 Lattice stiffening girders (N Truss) Lattice stiffening girders (N Truss) Lattice stiffening girders (N Truss) Lattice stiffening girders (N Truss)

At top of door level, these run longitudinally along both side elevations of thehangar.

3.3.8 Doors Doors Doors Doors

Each door measures approximately 10.7m high by 8 metres wide and weighs in theorder of 12.5 Tonnes. They comprise a series of 10” x 3” channels and 10” x 41/2”RSJ’s, which are externally sheeted in steel plate of varying thickness as follows:1/4” plate up to 6m high and 1/8" plate above. Originally, windows were fitted above8.4m height, but these have frequently been replaced with steel plates. Internally thedoors are sheeted in 1/2 " steel plate but only up to 6m height. Doors havesometimes been filled with gravel as blast protection.

In the original design it is apparent that the steel sheeting on both the frontand the rear faces on the door frames, are an integral part of the doorstructure. The steel plates provide strength and stability to the door framemembers, and in the case of the lower diagonal bracing members, act as thegusset connection plates.


December 2001 15151515

4 Structural appraisal

For the purpose of this Guide an initial structural appraisal was carried out for a typicalType C34 hangar using typical member sizes represented by the new drawings referred toin Section 3.2.2. The purpose of the appraisal was to examine the main components ofthe hangar type to check the hangar’s ability to carry the loading specified by currentloading codes. Structural calculations were undertaken in support of the appraisal.

The detailed findings of the appraisal are given later in the various sectionswhich follow. These findings are given purely to assist in the preparation ofoption studies. The refurbishment solutions given in section 7 are appropriatefor Option Study purposes providing that the site conditions, member sizes andloading circumstances are no less/worse than those considered in the appraisal.

Where member sizes and loading circumstances differ it will be necessary to undertakefurther appraisal work at option study stage in order to check the applicability of thesolutions offered in this Guide.

In any event, the progression to Project stage will require provision of detailed surveysand calculations in support of the chosen option.

It is recommended that where further appraisal work is undertaken the followingpublications are consulted.

• “Appraisal of existing structures” - 2nd edition, 1996 - I Struct E• “Appraisal of existing iron and steel structures” - SCI publication 138• “Assessing the capacity of existing steelwork” - SCI paper AD135• “Historical structural steelwork handbook” - BCSA

The remainder of this Chapter concentrates on the assumptions made in the appraisalprocess and the detailed findings. An indication is given of the process that a professionalcivil/structural engineer will normally take prior to advising on the structural adequacy ofa site specific Type C hangar and its proposed refurbishment.

4.1 DESIGN PHILOSOPHY DESIGN PHILOSOPHY DESIGN PHILOSOPHY DESIGN PHILOSOPHY

The calculations in support of the appraisal were carried out in accordance with thefollowing standards:

BS 449 1932 Use of Structural Steelwork in BuildingsBS 449 1937 Use of Structural Steelwork in BuildingsBS 6399 1996 Part 1 Loading for Buildings Code of Practice for dead and imposedloads

BS 6399 1988 Part 3 Loading for Buildings Code of Practice for imposed roof loadsBS CP3 Chapter V Part 2 1972 Code of Basic data for the design of buildings -wind loadsTICE 104 No 1986 Appraisal of existing and design of new runway and liftingbeams (then extant)

The appraisal calculations were undertaken to check the main structural members sothat informed professional judgement could be made of the adequacy of the genericType C hangar.



December 200116161616

The assumptions made in the appraisal of this generic Type C hangar may, due tosite circumstances, not translate to other Type C hangars.

The loading conditions, predicted future use, projected life span etc., will vary fromsite to site. It is recommended that, at Option Study stage, suitable allowances aremade for deviations from assumptions made in the appraisal used for this Guide andthat a site specific analysis is always considered before drawing any firmconclusions.

There are two extant British Standards which could be used in the design of steelframe buildings; namely BS5950 and BS449. Great debate exists as to which ofthese two codes is more appropriate for the analysis of historical structures. Finalselection is to be based upon professional judgement dependent upon the particularcircumstances of the structure and scale of project in question. Because this Guideis primarily to support the Option Study process it was considered that use of BSCP3 and BS 449 was appropriate.

For new Projects and for the refurbishment of Type C hangars the use of BS 6399and BS 5950 is considered to be appropriate.

4.2 MEMBERS ANALYSED MEMBERS ANALYSED MEMBERS ANALYSED MEMBERS ANALYSED

For the Type C34 hangar the following structural members were analysed:

Typical main girders type A, secondary trusses, columns, column foundationsrunway beams, vertical bracing and roof wind girders.

Amongst others, the following members were not checked:

Longitudinal edge beam, walls, parapets, purlins, doors, door supports and gantries;untypical members such as end trusses, C-38 cantilever trusses, C-38 main trusssupporting cantilever trusses, columns supporting end main trusses, C-38 columnssupporting cantilevered roof and associated untypical foundations.

The analysis for individual elements of the structure are described in Section 4.4.

The most heavily loaded portal frame was considered to be the central frame whichsupports two 6 ton runway beams. The beams span between the secondary trusses,one beam each side of portal frame (see drawing DE/H1/001/104).



December 2001 17171717

One typical frame was therefore checked as part of the appraisal consisting of:

Secondary trusses - span simply supported between main truss portals.

Main portal frame and - two cases were checked a) pinned feet portal;stanchions b) fixed feet portal.

Foundations - sizes on original drawings were based on a 2 ton persq ft permissible ground bearing.

it was assumed as part of the appraisal that baseshave been increased/decreased pro-rata to suitexisting ground conditions.

Vertical & Horizontal - this was checked on assumption that bracing Bracing one end only is taking full load.

4.3 BACKGROUND TO PERMISSIBLE STRESSES AND LOADING USED IN THE BACKGROUND TO PERMISSIBLE STRESSES AND LOADING USED IN THE BACKGROUND TO PERMISSIBLE STRESSES AND LOADING USED IN THE BACKGROUND TO PERMISSIBLE STRESSES AND LOADING USED IN THEAPPRAISALAPPRAISALAPPRAISALAPPRAISAL

The hangars were assumed to have been designed in accordance with the currentstandards of the day. BS449 (1932), BS449 (1937) and BS15 (1930). These statedpermissible working tensile stress of 8 tons/sq in (124N/mm2) and an ultimate tensilestrength of 28-33 tons/sq in (432-509N/mm2). The quality of steel has obviouslyimproved since those dates, therefore, the appraiser considered it prudent to checkthe structure on the original permissible stresses rather than compare with todayspermissible stresses.

The appraiser discussed with British Steel the method of design most appropriate tosteel of this age. It was suggested that limit state design was not applicable and,therefore, the steelwork was checked against the permissible working stresses ofBS449 1932.

Invaluable data on steelwork properties is summarised in the BCSA publication‘Historical Structural Steelwork Handbook’. Further guidance with particularemphasis on steel quality is given in the Steelwork Construction Institute paperAD135 - Assessing the capacity of existing steelwork.

Since 1932 , wind load requirements together with applied live loads have beensignificantly increased. In BS449 (1932) the wind force requirement was a standard15lb/sq ft (0.72KN/mm2) on vertical surfaces. The superimposed loading on roofswhich are inclined at more than 200 to the horizontal was 15lb/sq ft inwards onwindward slopes and 10lb/sq ft (0.48KN/m2) outwards on leeward slopes. Theseloads were deemed to include wind and were assumed acting normal to the surface.Superimposed loading on a flat roof was to be designed for 30lb/sq ft (1.44KN/m2).

The interpretation of the appraiser was that the hangar roofs were never designedoriginally to support any snow loading, only a wind force of 15lb/sq ft (0.72KN/m2)maximum normal to the roof surface.

Today, that same roof structure must not only be capable of sustaining a uniformsnow load but also be able to withstand local drifting of snow in the valleys althoughwith the drifting situation the current BS6399 does allow a reduced factor of safety.At the time of appraisal wind forces for the hangars were calculated in accordancewith CP3.

The appraisal calculations were originally prepared using the most onerous locationfor a hangar ie. Scotland. The findings indicated that the hangars were grosslyoverstressed. It was then considered that the loadings for Scotland were not reallycompatible with the location of the majority of hangars. The structure was,



December 200118181818

therefore, rechecked with loadings of a lesser magnitude taken for an area based inSouth Yorkshire/Lincolnshire where a large number of hangars exist.

A basic wind speed of 45m/s was, therefore, used in the calculation. A copy of thebasic wind speed map taken from Fig 1. of CP3: Ch V: 1972 is attached in Annex D.

Subsequent to the appraisal, BS6399 Part 2 has been issued and for Option Studypurposes only it is considered that loadings are unlikely to be significantlyincreased.

The initial intention had been to report on the general adequacy of the hangar ratherthan undertake a fully detailed structural analysis. However, due to the complexityof the various possible loading conditions the appraisal included a fairly rigorousanalysis. A single set of 1934 hangar truss detail drawings was used checking thedesign i.e. drg 861/35 and 865/35 as detailed in fig 3.2.

The section sizes were reproduced onto line details i.e. Drg No DE/H1/001/105 andDrg No DE/H1/001/106 refer.

The design check was carried out to these sizes. The findings are representative ofroof trusses made up of those members only.

A compromise between a fully detailed analysis and a cursory check was, therefore,undertaken. Forces and stresses in a typical 1934 hangar main frame and a singlesecondary truss were calculated based on two dimensional analysis only. Checkswere carried out on the riveted/bolted connection based on drawing No 865/35.

The structural members were checked and the working stresses compared with thebasic permissible stresses specified in BS449-1932.

BS449-1932, like the current BS449, allowed the permissible working stresses to beincreased to allow for wind loading.

The judgement was that there were reasonable factors by which the basicpermissible working stress could be increased when the structure is designed forwind loading conditions.

4.3.1 Wind loading

The appraisal check was in accordance with CP3:Ch V: 1972.

4.3.2 Snow and imposed roof loadings

Snow loading was applied in accordance with BS6399 : Part 3 : 1988.

Basic snow load, sb = 0.6 kN/m2

Assumed site altitude : less than 100m

4.3.3 Runway beams

The two different types of runway beam were individually checked for theirrespective capability to support 1.5 tonnes or 6 tonnes. In addition, for the generaldesign check of typical secondary trusses, a runway beam loading of 6 tonnes wasapplied. In the case of the main trusses, it was assumed that this 6 tonnes load couldbe applied simultaneously to both sides of the truss.



December 2001 19191919

4.3.4 Dead and services loading

A loading of 0.44 kN/m2 on plan was applied to allow for roofing materials andnominal building services.

4.4 OUTCOME OUTCOME OUTCOME OUTCOME

The appraisal found that for the locations considered in the study the Type C typestructure is capable of carrying loadings specified by loading codes at time ofappraisal. This is without excessive cracking or movement provided that thestructure was constructed as originally designed and had been maintained to areasonable standard.

This view was given based on a set of calculations for:

Runway BeamsSnow LoadingWind LoadingDead LoadingSecondary TrussMain FrameWind GirderVertical BracingColumnFoundations

and was based on:

Existing Air Ministry Drawings

2029/34 - GA Steelwork861/35 - Secondary Truss with 6T runway beam865/35 - Main Roof Girder Type A

The following loading cases were considered for the secondary and main rooftrusses.

Load Case B1. Runway Beams Loaded each side of trussLoad Case B2. Runway Beam Loaded at one side of trussLoad Case B3. Local Snow Drifting in ValleyLoad Case B4. Uniformly Distributed Snow LoadLoad Case B5. Net upward wind forceLoad Case B6 Net Downward wind forceLoad Case B7. Dead Weight from Secondary TrussesLoad Case B8. Structural Self Weight

The member dimensions used in the appraisal have been included on the new DEdrawings. (Sect 3.2.2).

The findings of the appraisal do not extend outside the defined geographical areareferred to earlier, or outside the assumptions made in the appraisal.

4.4.1 Secondary roof trusses

These trusses form the valley gutters and span between the main trusses. The trussesalso support the lifting beams which traverse the width of the hangar.



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Appraisal calculations indicated that under all loading conditions above, thestructural members of this truss are acting within the permissible increased workingstresses. This is based on the structural sections shown on the Drg DE/H1/001/106reproduced from original Air Ministry Drg No 861/35, which is for the trussproviding support for the heaviest lifting beam (i.e. 6 ton capacity). Some memberson other unchecked trusses are of smaller section but support lifting beams of 1.5ton capacity.

4.4.2 Main roof trusses

These trusses span the full width of the hangar, acting as a portal frame with theperimeter columns. The trusses support the secondary trusses spanning in between.

The appraisal found that:

1) Bottom Boom Member - satisfactory under all conditions.2) Internal Vertical Members - satisfactory under all conditions.3) Internal Diagonal Members - satisfactory under all conditions.4) Top Boom Member - does not exceed the limit of increased permissible

working stress under the load cases defined in clause 4.4.5) Main truss connections - Structural connections were considered from the

original Air Ministry drawing No 865/35. It was judged that for the purpose ofthe study there were reasonable factors by which the stresses could beincreased when the structure experienced wind loading. It was concluded thatsite based information should be used to confirm the adequacy of connections.

4.4.3 Runway beams

2 No 10” x 4½” x 25 lb/ft RSJ runway beams traverse the width of the hangar. Theyspan between the secondary trusses and are required to support a SWL of 11/2 tons.

Similarly 2 No 10” x 6” x 40 lb/ft RSJ with an additional top flange plate providesfor runway beams capable of supporting a SWL of 6 tons.

Both sizes of beams were considered to be capable of sustaining their appliedloadings subject to the adequacy of the connections.

4.4.4 Roof wind girder

2 No wind girders span the width of the hangar and are located one at each end.

These were found to be adequate to resist the wind forces calculated toCP3:ChV:1972.

The members normal to the top and bottom booms were checked on the assumptionthat they are providing an intermediate vertical support for the self weight of thediagonal members. This additional loading was still within the allowed increase topermissible working stress .



December 2001 21212121

The total wind load on the end of the hangar was assumed to be taken by a singlewind girder. The wind girder at the opposite end was ignored.

4.4.5 Vertical bracing

There are 4 No sets of diagonal vertical bracing, 2 sets per side of hangar.

A pair of wind braces at one end of the hangar were found to be adequate to safelytransmit the total wind forces to the ground.

4.4.6 Steel stanchions

These consist of 2 No 15”x6”x45 lb/ft Universal Beams, diagonally laced togetherand encased in concrete.

The columns have been analysed as pinned and then as fully fixed at their base toestablish the two boundary conditions and, mindful of the extent to which they areencased in concrete, the stresses were considered satisfactory under the encasedcondition.

4.4.7 Foundations

The information available was a standard drawing based on a permissible groundbearing pressure of 2 tons/square foot now reproduced at Drg DE/H1/01/102. Anote on the original drawing stated that the bases should be designed toaccommodate the permissible ground bearing at the individual location.

Calculations were carried out on the foundations sizes based on the 2 tons/squarefoot permissible bearing pressure.

The bases were adequate for vertical loading, but once bending moments wereintroduced, the ground was theoretically overstressed. No information on actualbase sizes was available for specific locations.

It was noted that there had been no reports of foundation failure. It was reasonedthat since the hangars had presumably been exposed to extremes of loading at sometime during their sixty years of life, and that no adverse effects had been recorded,then engineering judgement must be that the foundations have proved capable ofsustaining the actual forces applied.

It was recorded that holding down bolts were acceptable, and capable of taking thewind forces.

4.5 CONCLUSION CONCLUSION CONCLUSION CONCLUSION

Based on the findings of the appraisal, DE's conclusions are

1) that structural capability of the hangars to carry current day loading (ie. CP3 atthe time of appraisal) can be considered adequate for the locations covered.Outside the 45 m/sec basic wind speed contour eg. Yorkshire, Cornwall,Wales, the wind and snow loadings increase and where an overstress could beconsidered acceptable elsewhere it is unlikely that the other hangars (especiallyin Scotland) can be justified. However, it is reasoned that since all calculationsin the above appraisal had been based on a very restricted number of detaildrawings it is likely that the other hangars have been designed for the moreonerous local conditions.

2) the Northern hangars are still standing after 60 years and this is an indicator foruse in professional appraisals.



December 200122222222

3) the trusses have proved the test of time of 60 years and provided the membersare adequately maintained and repaired, the trusses should continue to providea structurally sound roof support.

4) the stanchions appeared to be approaching maximum increased permissibleworking stress. It, therefore, seems reasonable to accept that the stanchions willcontinue to provide adequate support even with the loading requirementsextant at the time of appraisal.

5) there did not appear to be any record of severe settlement occurring to thehangars, especially to the hangars in the area previously covered by what wasonce the PSA North East region on whose records the appraiser's report hasbeen based. It was not possible to confirm that the foundations are adequate.One original standard foundation drawing was found but this was based on a 2tons/square foot bearing capacity with the proviso that all locations shouldhave their foundation redesigned to suit the relevant conditions. Calculationsshowed that these bases could be overstressing the ground during exceptionalloading conditions at short duration.

6) in summary, it is proposed that for option study purposes the Type C hangarsare structurally sound, and capable of sustaining current loading conditions.This view relates to the main structural members and the information is basedupon a single set of standard drawings with the assumption that all hangarsconsidered had been constructed to equivalent details, or to enhancedrequirements commensurate with the loading at their location.

7) individual Option Studies for specific locations will require an appraisal of thebasic structure to confirm it is adequate for the actual loadings.

4.6 IMPLICATIONS OF APPRAISAL CONCLUSION IMPLICATIONS OF APPRAISAL CONCLUSION IMPLICATIONS OF APPRAISAL CONCLUSION IMPLICATIONS OF APPRAISAL CONCLUSION

It is, therefore, considered that the findings are appropriate for use at Option StudyStage. The preparer of a future Option Study should make suitable adjustments tocover:

a. actual geographical locationb. actual type of hangarc. actual knowledge of member sizesd. changes to loadinge. changes to wind codes issued subsequent to the appraisalf. changed understanding of how pre-war steelwork performsg. removal of wind speed limitations covered by TB 99/29h. changes to suit temporary condition of loadings


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5 Operational requirements

5.1 INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION

Like the majority of hangars on the MOD estate, the Type C hangar is currentlysubject to various operational requirements, in relation to concern about structuralsafety for heavy snowfall and high wind situations.

5.2 HANGAR BUILDING HANGAR BUILDING HANGAR BUILDING HANGAR BUILDING

The general structural appraisal identified that there are circumstances when thestructure of a Type C hangar may have the normal structural safety factors reducedto levels of concern eg. during complete door removal or introduction of dominantopenings in the end quarter of the gable elevations.

The onus is, therefore, on the EWC undertaking technical inspections andprofessional appraisals to identify site specific matters which may require furtherconsideration.

The appraisal was undertaken using a basic 3 second gust wind speed of 45m/sec astaken from and applied in accordance with CP3

For locations with a basic wind speed above 45m/sec eg., Scotland, Cornwall,Wales, Northern Ireland, and Yorkshire, the PROM will need to ensure that theEWC advises on the implications as part of the professional appraisal under DESpec 005. The EWC will, therefore, need to produce site specific guidance on thepermissible loading arrangements taking account usage of runway beams, heavysnow, high wind gust speeds, and the actual member sizes at the site concerned.

It is not possible in this document to give specific recommendations for each TypeC. This is because there are site specific matters to take into account.

eg. condition of structurebuilding orientationaltitudeweight of building services

In order to minimise further risk of overstress, the generic guidance is:

a) the load-carrying capacity of any runway or other lifting beamshould be certified and clearly marked on the beam (already an extantrequirement)

b) the adequacy of the supporting structure needs verifying as partof the professional appraisal

c) for hangars covered within the 45m/s wind speed contour the findings ofthis Guide may be used to supplement site based conclusion


5 Operational requirements

December 200124242424

d) keep hangar doors closed when winds are gusting at speeds of27m/s and greater, in accordance with Technical Bulletin 99/29

e) Keep hangar doors closed when high winds and heavy snow are forecastand do not use the runway beams

Users are advised to undertake Risk Assessments, to recognise both the financialand strategic value of equipment stored in hangars, and to appraise the significanceand implications of any potential loss. It may be necessary to devise an EmergencyAction Plan to protect valuable or important equipment from loss or damage.

5.3 PROFESSIONAL AND TECHNICAL INSPECTION PROFESSIONAL AND TECHNICAL INSPECTION PROFESSIONAL AND TECHNICAL INSPECTION PROFESSIONAL AND TECHNICAL INSPECTION

The current property management arrangements for hangars are contained in DESpecification 005. The EWC duties are:

Technical Inspection (Task 584) 2 yearlyProfessional Appraisal (Task 582) 5 yearly

It is recommended that the Technical Inspections have specific regard to the mattersraised in the documents and in particular the corrosion of structural frame eg.outriggers, corrosion of guttering, etc.

It is required that the outcome of the Technical Inspection is subject to review by aChartered Civil/Structural Engineer.

It is required that the Professional Appraisal is undertaken by a Chartered Civil/Structural Engineer and that the continued ability of the structure to perform itsfunction for the next 5 years be confirmed.

Where the EWC identifies areas of concern through either the TechnicalInspections, the Professional Appraisals or reports from others, the operationalimplications are to be considered by the Property Manager. In the event of concernthe precautionary measures should follow the typical scenarios established by theTB 99/29 see Annex E eg. site specific measures to be taken during snowfall, beforeand during high winds. Emergency action plans are required to cover these andother situations.


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6 Refurbishment - General

6.1 INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION

Refurbishment is normally the most economical and practical solution for a Type Changar, rather than demolition and new build. The main elements of work to beconsidered are roofing and gutters, vertical cladding (1938 version only), windows,walls and doors. It may also be necessary to repair or renew the ground floor slab tosuit loading requirements. Although the mechanical and electrical services usuallyalso require repairs or renewal, this is outside the scope of the Guide, however, suchwork should be considered at the same time as the main building work. The full lifecycle implications on maintenance, operation and efficiency are to be taken intoaccount. Each refurbishment option is to consider heating losses and ventilationrequirements.

6.2 OPTIONS AND RECOMMENDATIONSOPTIONS AND RECOMMENDATIONSOPTIONS AND RECOMMENDATIONSOPTIONS AND RECOMMENDATIONS

For any refurbishment project, an Option Study needs to be carried out in order toestablish the most cost effective solution. Reference should be made to BS 7543 :1992. Guide to Durability of Buildings

In carrying out such a study, the generic information contained within this Guide isto be quoted with any departures highlighted. This base information can include theform of construction, as shown on the drawings in Annex A (a).

The Budget cost estimates for Option Study purposes for the various roof optionsare given in Annex I. These can be quoted and updated to suit current requirements.

The choice of roof configurations and roofing material is usually a major constituentof any refurbishment project, and accounts for the largest expenditure item.

Every Option Study is to include the 'Flat Roof' Option. A review of recent optionstudies for a number of sites, where different methods have been used, therecommendations for the main roof element is to provide a 'Flat Roof' system,incorporating either a single ply membrane or the aluminium standing seam system,depending upon the life span required.

Further details of the separate refurbishment options for all of the elements aredetailed in the chapters dedicated as follows:

Roofing (Chapter 7)Gutters and Drainage (Chapter 8)Windows (Chapter 9)Walls (Chapter 10)Doors (Chapter 11)

Each element of work will be considered separately and where necessary detailedguidance will be covered in a relevant Annex.


6 Refurbishment - General

December 200126262626

6.3 WARRANTIES/GUARANTEESWARRANTIES/GUARANTEESWARRANTIES/GUARANTEESWARRANTIES/GUARANTEES

The installation of manufactured products can often be accompanied by a warrantyor guarantee. An examination is required of the associated terms and conditions toestablish the extent of any caveats. A check should also be carried out on anyexisting warranties that may still be in force from any previous works. If suchwarranties do exist, then continued applicability needs to be confirmed.

A further indication as to the credibility of an installed system can be demonstratedthrough accreditation by an independent testing house such as the British Board ofAgrément.

Careful consideration should be given to any conditions which tie MOD tocontinued involvement with the installing or supplying company. Such conditionsmay act to the long term financial detriment of MOD and may adversely affect theability of the EWC/WSM to effectively undertake their duties.

Where a guarantee is regarded as appropriate, it should be fully underwritten andinsurance-backed. For building systems comprising a number of products such asroofs or windows, guarantees should cover a whole system as installed including allfixings, sealants, glues, jointing systems, cut edges or any other treatment to thematerials necessary for installation. It is also essential to consider the extent,frequency and cost of any inspections or maintenance necessary to ensure continuedvalidity of the guarantee.

A quality installation is one which incorporates good design and skilledworkmanship. It is, therefore, important that full attention is given at the outset. Theguarantee/warranty is normally a confirmation of that process. In the event of afailure it is very unlikely that the guarantee/warranty will cover other than thebuilding work. The costs of disruption will normally still fall to the user.


December 2001 27272727

7 Refurbishment - Roofing

7.1 DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION

Original Type C hangars have multi-pitched roofs separated by valley gutters at7.62m (25ft) centres. With the exception of the earliest 1934 Type-C hangars, theend of each duo-pitch roof is hipped and rainwater run-off is collected by edgegutters behind parapet walls along each side of the hangar. Each internal valleygutter links with the edge gutter. In the earlier 1934 variations, the end of each duo-pitch roof is gabled without the edge gutter and all rainwater is collected by thevalley gutters which are not linked.

7.2 PROBLEMSPROBLEMSPROBLEMSPROBLEMS

a) The roof arrangement of a typical 300ft x 150ft 1934 hangar involves some2200ft (670m) of gutters, comprising 1650ft (503m) of valley gutters and 550ft(167m) of perimeter wall gutters. The entire system has no overflowcapability, resulting in blockages causing unacceptable discharge into thehangar building. Maintenance of the roof and gutters is of crucial importanceif overflow problems are to be avoided.

b) The internal cast iron rainwater down-pipes and underground drainage requiremaintenance if internal flooding due to pipe blockage and joint leakage is to beavoided.

c) The multi-pitch configuration produces potentially high snow loads whendrifting arises in the valleys.

d) The multi-pitch roof configuration includes a large number of hip and ridge tileruns, as well as numerous awkward flashing arrangements. These are areas offrequent maintenance and also add to the cost of re-roofing works.

e) The original 1930's roof construction comprises asbestos cement tiles orcorrugated sheeting fixed to timber battens on close boarding and supported bytimber purlins spanning onto the secondary trusses. After some 60 years, thefinishes are normally in need of replacement.

f) There is a significant amount of heat loss through the original multi-pitch roof,arising from:

1) ventilation via the valley gutters2) lack of insulation, and3) large surface area of roof because of the multi-pitch arrangement.



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7.3 ROOFING REQUIREMENTSROOFING REQUIREMENTSROOFING REQUIREMENTSROOFING REQUIREMENTS

Other than the obvious requirement for a roof to resist water leakage, the followinggeneral requirements apply:

Fire rating

The roof construction shall comply with Crown Fire Standard E10. In summary, thematerials must be self-extinguishing and must resist penetration by fire or hotairborne debris either from within or outside the hangar. This has two objectives:

• any fire within the hangar is contained and does not spread to other adjacentbuildings

• fire occurring outside the hangar cannot penetrate the roof and spread toareas within the hangar which may be protecting valuable equipment

Existing Type C hangars have dispensation regarding requirement for internalspread of flame (Sect 19 of Technical Bulletin 99/31).

Colour

For hangars, the roof colour is rarely of aesthetic importance. However, in thevicinity of airfields, very light colours can create a dazzling hazard being highlyreflective of sunlight. Conversely, dark colours absorb more heat which hinders thecontrol of internal temperatures within the building and the greater range oftemperatures increase thermal stress on materials. A medium but dull shade ispreferred, but as light as is acceptable to flying operations.

The Sponsor should confirm the requirement.

Durability

The proposed lifespan should meet the needs of the user. As discussed under"Warranties" in section 6.3, care must be taken to ensure that all components of aroof system have the same required lifespan including all fixings, sealants, glues,jointing systems, cut edges or any other treatment occurring during installation.

Independent accreditation

The roof system should have accreditation by an independent testing house, such asthe British Board of Agrément or other European equivalent.

Thermal insulation

The minimum requirement is to raise that element being refurbished up to thecurrent standards.

Investment appraisal techniques can be used to indicate that, to spend to save isjustified by increasing the thermal efficiency of the roof and other elements.

Lightning protection

Lightning protection needs to be considered as part of the refurbishment. There is arequirement to carry out a risk assessment for the structure to determine whether thestructure needs protection.

BS 6651 : 1999, provides a mathematical risk analysis method, which considers, thegeographical location, effective collection area, use of the structure, type ofconstruction, contents, location and topography.



December 2001 29292929

Non-metallic roofing systems normally require a network of air terminations, whichlink into the existing structure, and require down conductors to achieve earthing.

Metallic roofing systems do not normally require the networks of air terminations,but links to the existing structure, down conductors and earthing are required.

Careful design and attention to detail is vital to the successful installation of theprotection system.

7.4 ROOFING MATERIALROOFING MATERIALROOFING MATERIALROOFING MATERIAL

Materials

There are several roofing materials/types which may be considered:

A) single ply membrane, for which there are various different materialsB) standing seam concealed-fix aluminium sheetingC) traditional profiled steel sheetingD) traditional profiled aluminium sheetingE) composite sheetingF) fibre cement sheetingG) existing asbestos cement sheeting retained, repaired and coated with

waterproof compound.

Annex F provides further information on these and includes comprehensivereferences.

• A) to D) are used as part of built-up roofing systems comprising a series ofseparate layers, including liner sheets, vapour control membranes andinsulation, all assembled on site.

• E) comprises manufactured panels of sandwich construction effectively pre-assembling the liner sheets, insulation and external sheeting together off site.

• F) and G) involve labour intensive work on site. Neither lend themselves toproviding additional insulation, unless placed to the underside of the roofwithin the hangar (not always a practical solution) and not preferred due topossible condensation problems.

The above materials have different degrees of flexibility for how they may be usedin roofing solutions.



December 200130303030

7.5 ROOFING OPTIONSROOFING OPTIONSROOFING OPTIONSROOFING OPTIONS

There are many different materials which may be utilised to refurbish a Type C roof.When these are combined with the different possible roof layouts and roofingtechniques the options and sub-options for roof refurbishment are limitless. Anymajor roof refurbishments should replace all existing fragile roofing materials. Overthe years, many different methods have already been utilised on MOD's hangars andan examination of these together with a detailed study of particular solutions haveidentified that four options are considered. Option R1 – Flat Roof is the DErecommended solution. The latter one R4 represents poor value for money

Option R1 - Flat Roof (DE Recommended Solution)

R1a - Flat roof single ply membraneR1b - Flat roof aluminium standing seam

Option R2 - Multi Pitch Roof

R2a - Multi pitch roof built-up steel claddingR2b - Multi pitch roof built-up aluminium claddingR2c - Multi pitch roof composite steel cladding

Option R3 - Multi Pitch Retain Patch and Repair

Option R4 - Repair and coat original sheeting with a waterproofcompound

At major refurbishment, the DE recommended solution is a Flat Roof utilising eitherOption R1a single ply membrane or Option R1b aluminium standing seam,depending upon the projected life requirement for the hangar and a detailedinvestment appraisal to suit the specific requirements of the hangar.

Problems with 'flat' roof options at particular coastal sites have been reported to DE.These relate to the likelihood of birds being attracted to 'flat' roofs for nesting orroosting. Therefore, the advice is to consider any existing local problems, and thelikelihood of this been increased due to any refurbishment project. Particular adviceshould be sought from the relevant authorities at option study stage, such as theBirdstrike Avoidance Team. The retention of the multi pitch roof has manytechnical and financial disadvantages, but may in certain circumstances be retainedto meet a site specific requirement to retain external appearance. Where Option R2is specified the PROM should ensure that all the implications of retaining the multipitch roof are fully understood and included within the full life costings.

Option R3 should only be considered as a short term low reliability solution and isnot recommended.

Option R4 is not recommended and represents poor value for money.

Annex F contains details of many of the different roofing systems examined, but theremainder of this Chapter is dedicated to the above options.

At major refurbishment, the DE recommended solution is, therefore, Option R1.Provide new Flat over-roof. ie. this has the advantages detailed under 7.6.

Should individual sites have a long term specific wish to retain the multi-pitchconfiguration ie. Options R2 and R3, the Guide indicates other matters for fullconsideration.



December 2001 31313131

7.6 DETAILED DESCRIPTION OF ROOFING OPTIONSDETAILED DESCRIPTION OF ROOFING OPTIONSDETAILED DESCRIPTION OF ROOFING OPTIONSDETAILED DESCRIPTION OF ROOFING OPTIONS

The options are now described in detail together with drawings for illustrativepurposes only.

7.6.1 Option R1: Flat over-roofThe shallow fall provided by this solution requires that the roof is finished either inmaterial A (single ply membrane) or B (standing seam conceal-fix aluminiumsheeting).

For this concept all of the existing cladding, boarding and timber purlins areremoved, (providing the stability of the secondary truss members are not affected),but the steel structure is retained. The new roof is formed by spanning steel beamslaid to a fall, and supported off steel stubs at the main truss node points, (some ofthe steel stubs may require stability bracing). Cold rolled purlins at centres to suitproposed cladding. These span across the 7.62m centres of the trusses, carrying apitched roof typically to a fall of 1 in 40 (2.5%). This fall raises the roof by about600mm above the existing along the centre of the hangar.

The roof liner sheeting should be galvanised for durability or may be in aluminiumfor material B. A brighter internal working environment can also be provided if theliner sheeting is colour coated in a reflective light colour such as white.

Guide to World War II Hangars03 - Type C hangar


December 20032323232

FFFF Figure Figure Figure Figure 7.2 7.2 7.2 7.2 Option R1 Secondary truss detailsigure 7.1igure 7.1igure 7.1igure 7.1 Option R1 Main truss details

Main roof girder truss

New flat roof profile

Gutter

Lattice stiffening girder

Purlins on stub columns

LacedColumn

¢

LacedColumn

¢

Figure Figure Figure Figure 7.1 7.1 7.1 7.1 Option R1 Main truss details

1



December 2001 33333333

Stub co lum n.

Cold ro lled purlin

F la t roof over compris ing e ither single ply m em brane or a lum in ium standing seam sheeting w ith insu la tion on vapour contro l layer and profiled lin ing panels.

S econdary truss spanning 7.62m between m ain trusses.

Figure Figure Figure Figure 7.2 7.2 7.2 7.2 Option R1 Secondary truss details

The advantages of roof option R1 are as follows:

a) all valley gutters are removed which

• removes the cost of valley gutter renewal both initially and in thefuture; (gutter replacement intervals often differ from those forroofs)

• removes a major ongoing maintenance liability

• removes the possibility of valley snow loading occurring

• removes a source of likely leakages arising from overflow due toblockages

• removes the air loss via the valley gutters - a main source of heatloss

b) compared to the multi-pitch arrangement, the flat roof concept reduces theoverall surface area of roof, thereby:

• reducing the cost of the roof, due to use of less materials

• reducing heat losses, due to reduced roof area

c) with both the membrane and standing seam solutions, no fixings or sealantsare exposed to the external hostile environment, thereby:

• minimising the maintenance requirement

• minimising the risk of roof component failure



December 200134343434

The disadvantages of option R1 are as follows:

a) the need for some additional supporting structural steelwork, and for deeperpurlins to span between the main trusses

b) due to removal of purlins on the secondary trusses the stability of themembers under compression will need to be checked as part of the designprocess and additional provision made for lateral stability

c) marginally longer construction period than option 2

d) the ability of the roof drainage systems to hold water is reduced thus leadingto quicker run off with possible flooding consequences

e) it will require total possession of the hangar

7.6.2 Option R2: Multi-pitch profile, removing existing timber boards

This option retains the existing multi-pitched roof profile, and reclads the roof inbuilt up steel or composite cladding. It assumes that the condition of the existingtimber boarding and purlins necessitates their removal.

New purlins are provided spanning about 7.62 m between the secondary trusses.These support new liner sheets, insulation and new roof covering as per the desiredmaterial option. The liner sheeting should be galvanised for durability unless inaluminium. A brighter working environment can also be provided if the linersheeting is colour coated in a reflective light colour such as white.

If the gutters are more than five years old it would normally be cost effective to alsorenew all valley and perimeter gutters at the same time to aim for compatible lifespans. Renewal periods for gutters and roof materials often differ, and access forfuture gutter work can be limited if the roof is to remain undamaged.


a) the external appearance of the building remains largely unchanged

b) materials A and D may be used, offering a similar lifespan to roof option R1

Disadvantages of roof option R2 are:

a) the valley gutters remain, with consequences to renewal and maintenancecosts, disruption at future gutter renewal, risks of leakage, and valley snowloading. Heat losses are not reduced

b) the multi-pitch arrangement requires:

• greater cutting of roof sheeting, thus increasing labour and materialwastage costs

• greater detailing arrangements for ridge, hip and flashing



December 2001 35353535

7.6.3 Roofing Option R3: Multi-pitch profile, retaining existing timber boardingThis option is very similar to roof option R2, except that the existing timberboarding and purlins remain. There may be a need for some local repair andpartial renewal of deteriorating timber. All timber, new and retained, should befully treated with a solvent based preservative for rot and insect attack.

To support the new overlying sheeting, new metalized purlins will be placed on theboarding with fixings through into the timber purlins beneath. The depth of thenew metal purlins is usually determined by the insulation thickness and ventilationgap, rather than a spanning requirement. Insulation is supported directly by theretained timber boarding, in lieu of providing new liner trays.

It is preferable to review all valley and perimeter gutters at the same time as majorroofing works, thus aiming for compatible lifespans. Future gutter replacement canbe very difficult, is disruptive for the occupants below and can cause damage to theroof.

P ro file d m e ta l ro o f sh e e t in g w ith in s u la t io n o n v a p o u r c o n tro l la y e r .

E x is tin g b o a rd in g re ta in e d a s lin e r to b e re p a ire d a n d p re s e rv a t iv e tre a te d .

N e w c o ld ro lle d p u rl in s b o lte d th ro u g h b o a rd in g in to e x is t in g t im b e r p u r lin s .

S e c o n d a ry tru s s s p a n n in g 7 .6 2 m b e tw e e n m a in tru ss e s .

Figure Figure Figure Figure 7.37.37.37.3 Option R3 Secondary truss details

The advantages of roof option R3 are the same as for option R2 with the addition ofthe following:

a) a cost saving is made by retaining the existing timbers

b) the construction period is marginally shorter than for other options

c) by retaining the inner boarding, there is less disruption to the occupancy ofthe hangar during refurbishment.



December 200136363636

Disadvantages of roof option R3 are the same as for option R2 but the followingadditional matters must be considered:

a) the lifespan of the roof is dependent on the adjudged longevity of the retainedtimbers

b) the need for additional timber repairs may be uncovered during therefurbishment work, resulting in extra costs, possible delays and potentialcontractors' claims.

7.6.4 Roofing option R4: Repair and coat original sheeting with a waterproofcompoundWhere a defective roof needs making good for a short term, eg. less than fiveyears, a proprietary overlay or patch repair system may be considered. If thegutters are in a poor condition, their repair should be considered prior to theapplication of compound, because subsequent repair would be very disruptive andpotentially damaging to the existing roof.

Wholesale gutter replacement and renewal is not advocated for this short termsolution.

E x is tin g s h e e tin g re ta in e d , to b e c le a n e d , re p a ire d a n d c o a te d w ith a p ro p rie ta ry w a te rp ro o f c o m p o u n d . E x is tin g b a o rd in g a n d tim be r p u rlin s re ta in e d .

S e c o n d a ry tru s s s p a n n in g 7 .6 2 m b e tw e e n m a in tru s s e s .

Figure Figure Figure Figure 7.47.47.47.4 Option R4 Secondary truss details


a) the construction period is shorter than that for Option R1

b) there is limited disruption to the occupancy of the hangar during the work.



December 2001 37373737

The disadvantages of roof option R4 are:

a) it is very expensive compared to the other options

b) the lifespan of the roof is short and is dependent on the old timbers andcondition of asbestos cement. It should not be regarded as a permanentsolution. It gives very poor value for money

c) unless insulation is provided in some other way, this roof construction willlose heat quicker than through the other options

d) being covered by the asbestos sheeting, the underlying timbers will be difficultto effectively treat with a suitable preservative

e) the need for additional timber or sheeting repairs may be uncovered during thework, resulting in extra costs, possible delays and potential contractors' claims.

7.6.5 Matters to be considered with all options

• efficiency in use especially long term maintenance, heating costs, etc.• roof access• lightning protection• disruption during works.

7.7 SUMMARY OF ROOFING OPTIONS SUMMARY OF ROOFING OPTIONS SUMMARY OF ROOFING OPTIONS SUMMARY OF ROOFING OPTIONS

OPTION R1 Provide new flat over-roof: using either a single ply membraneor standing-seam aluminium sheeting, including new purlinsand insulation.

OPTION R1 IS THE RECOMMENDED OPTION.

OPTION R2 Retain existing multi-pitch roof profile: Remove existingtimber boarding, and reclad with new profiled metal sheeting,purlins and insulation.

OPTION R3 Retain existing multi-pitch roof profile: As Option R2, butretain and repair existing timber boarding.

OPTION R4 Retain existing multi-pitch roof profile: Clean, repair and coatexisting sheeting with a waterproof compound.

A tabulation of these options is given at Annex F.



December 200138383838


December 2001 39393939

8 Refurbishment - Gutters and drainage


Gutters constitute a major weakness with the traditional multi pitch Type C roof. Atmajor refurbishment, every effort needs to be taken to ensure that this, oftenoverlooked and trivialised area, is properly addressed and an adequate solution fullydeveloped and specified.

The original gutters were typically 455mm wide by 155mm deep, and constructed in5mm thick galvanised mild steel. Subsequent maintenance may have involved thepainting or covering in bitumen sheeting or other waterproofing material. There is aparapet gutter 84m long to each side of the hangar, and a series of valley gutterseach 46m long within the multi-pitch arrangement. The 1934 version has 12 valleygutters (552m total length), and the 1938 version has 11 valley gutters (506m totallength) but with eaves gutters, each 46m long above each end door. The valleygutters discharge into the parapet gutters, which, in turn, discharge into a series of152mm diameter cast iron down-pipes, typically 11no. on each side of the hangar.

Refer to Sect 7.2 for additional generic description of the multi-pitch roofarrangements and valley gutters.


The original mild steel gutters have lasted well but will now have normally exceededtheir useful life, with corrosion sometimes having perforated right through the steelplate.

Gutters are prone to blockages due to self-sown vegetation, wind-blown debris, deadbirds and dropped maintenance items. In the event of a blockage or short periods ofhigh rainfall, the original roof and gutter design allows a surcharged gutter tooverflow under the edge of the roof into the building. With the multi-pitched roofarrangement, this problem can result in water spillages anywhere in the hangar.

In addition, with no local widening to form a tapered hopper-head at the tops of thedown-pipes, the outlet flow is limited and the gutter-efficiency reduced. In order togenerate the discharge required of high flow conditions, the gutter fills to a greaterdepth and the freeboard is much reduced.

It has been known for inappropriate and poor maintenance work to have laidbitumen sheet over some rainwater outlets, thereby forcing the stormwater dischargeto flow through a reduced number of outlets and down-pipes. Due to the resultinglack of capacity, the gutters become surcharged and overflow into the building.

Although some gutters can last perhaps 30 years, inappropriate joint sealants fail atmore frequent intervals.



December 200140404040

The original below-ground drainage needs to be maintained and kept clear. Thestructural adequacy of underground pipelines needs to be checked and their capacityascertained as part of any major refurbishment work.

8.3 GUTTER PROPOSALS GUTTER PROPOSALS GUTTER PROPOSALS GUTTER PROPOSALS

Gutter renewal periods usually differ from the roof coverings, however, gutterreplacement by itself is often disruptive to an existing roof construction.

Where roof replacement/refurbishment is carried out it is recommended that gutterreplacement is done at the same time.

8.4 GUTTER MATERIAL OPTIONS GUTTER MATERIAL OPTIONS GUTTER MATERIAL OPTIONS GUTTER MATERIAL OPTIONS

The main materials for gutter replacement are:

• coated galvanised mild steel (original gutters lasted for about 40 years;modern gutters are low cost but thinner with design lives of 10 to 25 years,low cost)

• aluminium (25 to 40 years, medium cost, needs good detailing andworkmanship to avoid bimetallic corrosion and to allow good provision forexpansion)

• stainless steel (expensive, 60 years plus)

• glass reinforced plastic (GRP), as a replacement or relining to existing

• single ply membrane, integrally with the roof system (material option A),also needing decking and side support

• reinforced bitumen or felt lining (short term) is effective for the short termonly, perhaps for 5 years and not more than 10 years and should only beconsidered when an Option R4 Patch and Repair solution is being used.

All relining work needs good workmanship and supervision. All options aresusceptible to impact damage, and use of snowboards will assist to protect; stainlesssteel has best resistance, then steel but coating/galvanising is susceptible and ifdamaged will reduce lifespan.

Design life is also governed by sealant durability and workmanship. It is very rarefor sealant to last 20 to 30 years. Coated galvanised steel is the preferred option fora traditional gutter.

The use of a single ply membrane as an extension of roof material option A isequally applicable.

Care is also needed in selecting an appropriate joint sealant, for whichmanufacturer's recommendations should be followed. Joint sealants need care in itsspecification and, workmanship on site. Provision should be made to accommodatethermal expansion of long gutter lengths.



December 2001 41414141

New gutter designs should incorporate adequate insulation to satisfy buildingregulations, reduce heat losses, and to stop condensation which causes internaldripping and can initiate corrosion. Composite insulated gutters will reduce thegutter capacity due to the thickness of the insulated gutter wall.

8.5 GUTTER ARRANGEMENT GUTTER ARRANGEMENT GUTTER ARRANGEMENT GUTTER ARRANGEMENT

There are two main alternatives for the perimeter gutter arrangement.

8.5.1 Renewal or re-use of existing internal down-pipes

Improve gutter system with the following:

• provide tapered hopper-heads with rounded edges, to improve dischargecapacity

• incorporate gargoyle-type overflow pipes to stop the gutter overtopping intobuilding

• in conjunction with the single ply membrane roof option, dress the membranein and around the gutter to form a sealed lining, thus, removing the provisionfor overtopping into the building

• renew the internal down-pipes. Consideration may also be given toproviding a siphonic system to improve the discharge capacity and reduce thenumber of down-pipes required. As the below-ground drainage would alsoneed renewing to cater for the increased flows, this option can appearexpensive. However, the underground drainage may be in need of majorreplacement due to other deficiencies.

G u tte r f la sh in g s .

E x is tin g tim b e r o n n e w m e ta l ze d p u rlin .

S n o w b o a rd s a n d s u p p o rts

R e m o v e e x is tin g g u tte r a n d re p la c e w ith p re fo rm e d in s u la te d m e ta l g u tte r o r s in g le s k in g a lv a n ise d g u tte r a n d s e a l a ll jo in ts .

E x is tin g g u tte r s u p p o rt fra m e .

F o rm 6 n o g u tte r o ve rsp ill s h u te s .

E x is tin g p a ra p e t c o n s tru c tio n e ith e r c o n c re te , b r ic k o r c la d d in g o n s te e l fra m e .

Figure Figure Figure Figure 8.1 8.1 8.1 8.1 Parapet gutter detail (edge protection not shown)



December 200142424242

G u tte r fla s h in gS n o w b o a rd .G u tte r s c re w e d to p a c k in g p ie c e s a t 9 0 0 c e n tre s o r f ix e d in a c c o rd a n c e w ith m a n u fa c tu re r 's in s tru c t io n s .

R e m o v e e x is t in g g u tte r a n d re p la c e w ith p re fo rm e d in s u la te d m e ta l g u tte r o r s in g le s k in g a lv a n is e d g u tte r .

R e m o v e e x is t in g p a c k in g a n d re p la c e w ith n e w ta n a lis e d p a c k in g to s u it fa lls .

Figure Figure Figure Figure 8.2 8.2 8.2 8.2 Typical section through Valley Gutter

8.5.2 Provision of new external down-pipes

Discharge parapet gutter through the parapet into external hopper-heads and providenew down-pipes external to the wall, discharging to new below-ground drainage.Where an annex is adjacent to the hangar, a new horizontal pipe may be providedexternal to the wall, to collect stormwater from the down-pipes for disposal at eachend. In this case, new below-ground drainage will be required to cater for the down-pipe discharge at each of the four corners of the hangar, as the current drainagelayout collects stormwater centrally in the middle of each side wall.

Alternatively, the external hopper-heads at high level could be connected to theexisting internal down-pipes via new swan-necked pipes.

Again a siphonic system may be feasible as the existing below-ground drainage willrequire renewing for this option, as discussed above.

8.6 SNOWBOARDS SNOWBOARDS SNOWBOARDS SNOWBOARDS

The original snowboards (also known as duckboards), were constructed in timber. Itis recommended that a system of snowboards is also retained for either arrangement.Their purpose is threefold.

Firstly, as the name suggests, they prevent a build-up of snow in the gutter. Anysnow in the gutter is less likely to contribute to blockages and resultant roof leaks.

Secondly, snowboards provide protection to the gutter from damage due to foottraffic or movement of equipment and tools during maintenance, for which the gutteris not always designed.

Thirdly, snowboards limit the build-up of wind-blown or dropped debris whichwould otherwise require more frequent maintenance to clear blockages.



December 2001 43434343

The original timber boards are likely to need renewal or replacement. For ease ofgutter maintenance, snowboards should be as light as possible to aid their handling,but with adequate means to resist the danger of wind uplift or becoming dislodgedand causing a trip hazard. Suitable materials are timber, glass-reinforced plastic(GRP), UPVC, aluminium or steel, the latter being rather heavy. For lightweightease of use and minimum maintenance, UPVC snowboards are likely to be the mostcost-effective in the long term. Various means of support are possible, but care isneeded to ensure that the gutter flow is not hindered:

• straps can be used to span across the gutter onto local purlins at centres tosuit snowboard strength and local bearing solutions

• the snow boards can be designed to span across the gutter sitting directly onthe roof edge

• stools can be provided to sit directly in the gutter, but of a thin profile tominimise restrictions on a free-flowing gutter.

The flat roof option R1 removes all valley gutters and thereby reduces the totallength of all gutters and associated snowboards from 670m to 167m. With a singleply membrane or standing seam aluminium extended across the roof edge anddressed fully around the gutter surface, consideration can be given as to whethersnowboards are needed. Full access requirements need to be addressed, as theremay be a need to attend to lighting, antenna or other equipment attached to thehangar roof. (See Section 12).

Where there is a desire to retain the existing sloping timber boarding and asbestoscement sheeting, the opportunity can be taken to consider use of walkways whichform a physical barrier to prevent people falling through any fragile membraneadjacent to the valley gutter.

8.7 BELOW-GROUND DRAINAGE BELOW-GROUND DRAINAGE BELOW-GROUND DRAINAGE BELOW-GROUND DRAINAGE

The condition of the drain runs and manholes should be checked. This may includea visual check plus close circuit television video footage appropriate to the diameterinvolved. It is advisable to ensure that the drain runs are cleaned prior to any CCTVsurvey.


8 Refurbishment - Gutters and Drainage

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9 Refurbishment - Windows


The original windows were of steel frames which in many cases have been replacedby Profilit glass units. The typical variations are:

1934: A window panel approximately 6.2m long by 4.4m high within each7.62m structural bay occurring wholly within a brickwork or reinforced concretewall requiring support by a R.C. lintel. With concrete walls, the lintel is formedintegrally within the wall.

1938: Window panels are set about 3m high but of varying length either 13.4mor 21.4m long running across two or three structural bays. There is no lintel supportas the walls are constructed only to the top of the windows, above which the hangaris framed in steel and originally clad in asbestos cement sheeting.


1. Differential movement between the glazing and the surrounding structure. Thecauses are:

a) thermal movement of the glass, window frame and wall material atvarying rates

b) concrete shrinkage

c) brickwork expansion due to moisture absorption

d) corrosion of steel window frames, and

e) inadequate provision of movement joints in the walls.

Because of the rigid and brittle nature of glazing along with the old windowdesign, maintenance problems are inherent.

2. Internal lighting conditions: Although natural lighting may have been anoriginal assumption, it will not always provide an ideal working environment.The lighting levels vary ie. sunlight to complete darkness at night. Brilliantsunshine can be dazzling and causes shadows giving an uneven lightingdistribution unsuitable for some types of working. Sunlight intensity is bothvariable and unreliable, the contrasting pattern of bright and shadowed areasalters during the day. Artificial lighting still remains necessary.

3. Heat losses due to inadequate old windows.

4. Absence of a means of controlling ventilation by opening windows.

5. Poor access for maintenance and cleaning.


9 Refurbishment - Windows

December 200146464646

6. Doubts about the ability of existing windows to withstand local wind loading.

9.3 PROPOSAL FOR WINDOWSPROPOSAL FOR WINDOWSPROPOSAL FOR WINDOWSPROPOSAL FOR WINDOWS

The Statement of Requirement (SOR) for a refurbished hangar will need to identifyactivities to be undertaken within the hangar. This will dictate the type of lightingrequired and the heating and ventilation requirements.

If natural lighting is required, it should be specified in the SOR with the knowledgeof its effect on the cost of window provision, window maintenance and anyassociated access requirements.

If natural daylight is not required for specific work tasks within the hangar it isrecommended that windows are not installed during refurbishment of buildings. AnInvestment Appraisal will need to identify the additional cost of providing naturallightning and justify its use. With modern high efficiency lighting, any additionalenergy required to light the building will be compensated by the increased thermalefficiency of the building, however it should be noted that attention to roof heatlosses will provide even greater scope for reduction. The security classification ofthe hangar will address the need for anti-blast glazing.

The glazing specification for new or major replacement work should consider DEDMG 02, Glazing Standard for MOD Buildings Subject to Terrorist Threat. Forany chosen window option, it will be necessary to examine the long term costs inuse, both operationally in terms of energy usage and in terms of maintenance andrepair.

There are four options available:

Option W1 Remove existing and provide solid infill, or overclad with suitableinsulated opaque cladding.

Option W2 Remove existing and replace with translucent wall cladding or multi-wall polycarbonate sheeting with suitable light diffusion, thermal anddurability characteristics.

Option W3 Remove existing window and replace with, perhaps, double glazedunits in appearance similar to existing.

Option W4 Retain existing windows if condition permits, and repair. Strengthenif required.

Option W1 Will provide the best value for money solution unless otheroptions are specifically required in the SOR.

Options W3 and W4 are available, but these are not recommended.

Annex G provides:

1. a summary of the advantages/disadvantages of each window option

2. illustrative detail of Option W2 - overcladding solutions for polycarbonate ortranslucent sheeting

3. illustrative detail of Option W4 - strengthening of existing glazing

4. detail of overcladding at existing window positions.


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10 Refurbishment - Walls

10.1 DESCRIPTION DESCRIPTION DESCRIPTION DESCRIPTION

The construction and elevational appearance of the existing walls varies, dependingon the hangar version, date built and occasional local variations. The main sidewalls of early 1934 versions were built in brickwork, and stone has been used forhangars in some area. There are cases where the masonry has been rendered.Reinforced concrete was used for the hangar walls, for the majority of 1938versions.

1934 HANGAR

Vertical asbestos cladding

Reinforced concrete wall

1938 HANGAR

Existing w indows.

Single storey annexe

250 reinforcedconcrete wall or 450solid brickwork

125 reinforcedconcrete wall or 279cavity brickwork

254 reinforced concrete wallor 279 cavity brickwork (335solid wall abutting annexe)


Figure 10.1Figure 10.1Figure 10.1Figure 10.1 Side Elevations as Existing

10.2 REINFORCED CONCRETE REINFORCED CONCRETE REINFORCED CONCRETE REINFORCED CONCRETE

The reinforcement is regarded as mainly for anti-crack purposes and is not normallyof major structural significance. The exception to this is the framing around doorand window openings, and the bottom 1.5m of the R.C. walls which are designed tospan between pad foundations. In contrast, masonry walls bear on strip footings.Asbestos cement cladding was used above the doors in the end walls of 1934versions, and above the windows in the side walls of 1938 versions.



December 200148484848

10.3 DETERIORATION OF WALLS DETERIORATION OF WALLS DETERIORATION OF WALLS DETERIORATION OF WALLS

Masonry/ This can vary significantly depending on the brick type used Brickwork and the degree of exposure to local atmospheric and

environmental conditions. With good periodic maintenance work,many walls should continue to serve their purpose. Others will needmore extensive treatment with possible areas of rebuilding.

Concrete Due to the poor grade of concrete used in construction and the lackof adequate cover to reinforcement, many hangars have concretewalls with cracking and spalling. The reasons for deteriorationshould be determined. Spalled concrete can cause problems foraircraft and is a safety hazard to personnel below.

Cladding In many cases, the existing sheeting is nearing the end of its usefullife. Repairs to asbestos cement sheeting can present a healthhazard.

10.4 ALTERATIONS ALTERATIONS ALTERATIONS ALTERATIONS

Caution is required when making structural alterations to hangars or annexes withconcrete walls. It is essential to remember that unlike masonry walls which bear onstrip footings, the R.C. walls are designed to span between individual columnfoundations. The R.C. wall beneath an annex window acts as a beam and, therefore,the structural significance of window enlargement, or conversion into a dooropening, should be considered.

The original construction provided inadequately for movement in masonry andconcrete walls. This cause of cracking and spalling may be addressed duringrefurbishment.

10.5 TREATMENT OF EXISTING CLADDING TREATMENT OF EXISTING CLADDING TREATMENT OF EXISTING CLADDING TREATMENT OF EXISTING CLADDING

Replace existing cladding with suitable insulated cladding. The areas of walloriginally clad in sheeting differ according to the hangar version:

1934: sheeted at both ends of hangar along its full width above the main doors.

1938: both sides of hangar sheeted along its full length above the windows.

10.6 PROPOSALS FOR SOLID WA PROPOSALS FOR SOLID WA PROPOSALS FOR SOLID WA PROPOSALS FOR SOLID WALLSLLSLLSLLS

In order to determine the repairs required, it is important to undertake preliminaryinvestigatory work to identify or confirm the causes of any deterioration. Failure todo this leads to inappropriate remedies at unwarranted extra cost to the client.Symptoms such as concrete spalling and cracking can result from various causes,and for the correct treatment to be used, the cause should be clearly identified.

Some degree of local material repair is usually necessary, together with otherpreventative action. Material repair alone is rarely economical for large areas.



December 2001 49494949

Masonry repairsMaterial repairs alone are rarely economical for large areas, other preventativemeasures are usually required such as over-cladding. Where masonry repairs arefeasible, care is required in matching new mortar with the existing. The use ofinappropriate mortars, very often, has a detrimental effect on the wall, as follows:

a) a poor colour match can make repair patches stand out like "sticking plasters"with large numbers of repairs giving the wall a patchwork appearance.

b) the wrong blend of mortar constituents can actually cause long term damage tothe wall, often accelerating the rate of deterioration. Ordinary modern mortarsare usually stronger than the original due to the properties of modern cement,and can cause the following situations:

1. repair patches are stronger than the locally surrounding wall and so have lessability to accommodate movement. Future movement is then limited toadjacent weaker areas of wall, thereby increasing the likelihood of crackingand the rate of deterioration in these areas.

2. normal modern mortar is usually less breathable than the original lime mortarand its use often impairs the behaviour of the masonry resulting in surface"blows" or disintegration.

Use of traditional lime mortars is often necessary.

Repairs to reinforced concrete wallsThe guidance given in the following BRE publications should be considered:

Corrosion of steel in concrete BRE Digest 444 Parts 1, 2, & 3 Feb 2000Repair and maintenance of reinforced concrete Currie & Robery 1994Corrosion Damaged concrete Pullar-Strecker CIRIA 1987

WallsAll external walls of a building envelope should be designed so as to provide thefollowing:

• a weatherproof skin

• thermal insulation as required by the Building Regulations

• physical security

• resistance to impact damage.

Wall claddingThe criteria for choosing a wall cladding system and the range of materials, finishesand insulation available are much the same as for roofing. Some variations arepossible:

• structural steel liner trays can be added, providing a flush inner wall

• it is necessary to ensure that any core material has appropriate fire resistance

• some cladding systems have the option of an industrial grade plasterboard, orcomposite plasterboard/insulant inner lining. These materials are not regardedas durable enough for most hangar facilities.



December 200150505050

Over-cladding of wallsExternal cladding is the recommended solution for deteriorated concrete andmasonry walls. The cladding serves at least three purposes:

• protection of the concrete from the weather and atmospheric borne agents ofcorrosion

• improvement to the insulation characteristics of the building

• protection of personnel from falling pieces of spalled concrete

The causes of deterioration must first be established and remedial works carried outbefore any decision is taken.

1934 HANGAR 1938 HANGAR


New wall sheeting to overcladexisting solid walls with ranslucent sheeting acrosswindow areas.


New wall cladding to replaceexisting and extend to overcladexisting solid wall. Translucentsheeting across window areas.

Figure Figure Figure Figure 10.2 10.2 10.2 10.2 Side Elevations as Proposed Flat roof option

Lower dado wallsThe lower dado walls provide:

• appropriate physical security against unauthorised entry (refer also to Sect13.4)

• simplicity for internal fixings

• simplicity or repair in the event of accidental damage

• greater ease of fire compartmentalisation.

A fully engineered design may dictate forms of construction commensurate with theheights involved. Guidance on the selection and suitability is provided in BREReport 262 Thermal Insulation Avoiding Risks. These walls should comply with therequirements of the Building Regulations in respect of structural stability, resistanceto damp penetration and thermal performance.

Increases in the height or thickness of walls may be dictated by acousticconsiderations, the requirements for fire compartmentalisation, or levels of increasedsecurity for specialist Units.

Care should be taken with the detailing, specification and construction of masonrywalls, particularly in areas susceptible to conditions of driving rain. Movementjoints should be provided in accordance with BS 5628 Code of Practice for the Useof Masonry.

New wall sheeting to overcladexisting solid walls withtranslucent sheeting acrosswindow areas



December 2001 51515151

Guidance publications:BRE Information Paper 19/81. Assessment of Hard Body Impact Resistance ofExternal Walls.BRE Report 262 Thermal Insulation; Avoiding Risks.

Re-alkalisation of concreteThis process restores carbonated concrete to its original alkaline state, which isnecessary for the protection of reinforcing steel. It can be very expensive, howeverit is said to be economical in the long term.

Corrosion protection (CP) systemsThese can also provide very effective means of controlling corrosion of thereinforcement, but again can be expensive to set up. In the long term, this system isinexpensive to operate and can use remote controls, ideal for sites with accessdifficulties. For hangars, solutions other than CP are regarded as more cost-effective.

Summary of wall repairsWalls are not usually considered to be critical structural elements which mightwarrant CP systems or realkalisation.

A system of basic repairs, anti-carbonation coating and overcladding is regarded asthe most effective.



December 200152525252


December 2001 53535353

11 Refurbishment - Doors

11.1 DESCRIPTION DESCRIPTION DESCRIPTION DESCRIPTION

There are six sliding and overlapping steel doors at each end of a typical Type-Changar. Each door measures approximately 10.75 m high by 8m wide and weighs inthe order of 12.5T, comprising a steel frame clad in steel plate. The doors run oncast iron wheels in tracks set into a reinforced concrete footing. The tops of thedoors run between guide rails which also provide lateral restraint. Originally, thecavity between the sheeting was filled with gravel, although there was an instructionin the 1950s to remove the gravel to reduce the load on the wheels.

11.2 PROBLEMS PROBLEMS PROBLEMS PROBLEMS

Water has leaked into the doors, resulting in corrosion of the door frame and theplates, exacerbated by the lack of ventilation in the door cavity and retention ofwater by the gravel infill. Expansion due to corrosion has occurred causing theplates to bow out between the fixing bolts or studs, leaving rust-filled gaps betweenthe frame and the plate. Around the edge of each plate these gaps allow furtherwater penetration, thereby, aggravating the situation, particularly around theperimeter of the doors.

The wheels and tracks have worn and corroded, often by 10 mm or more.

The lower tracks collect debris which can cause derailment.

Health & Safety Warning Notice 01/02 identified the shearing and corrosion ofmembers providing upper level lateral support to the door.

Subsequent investigations has indicated dubious shimming arrangements to theupper level lateral support bracket, often involving a 150mm depth of shims. It isrecommended that this detail is reviewed as part of any refurbishment.

The upper guide rails have also corroded particularly at the fixing brackets and boltswhere the rails are formed by channels lying flat or I-sections. Water and debriscollects on the exposed web and is contained by the upturned flanges. In some casesthis has been eased by the drilling of holes through the web, but the arrangementremains poor.

Due to wear and tear, corrosion, and a lack of maintenance, fixtures at height havebeen known to loosen and fall creating a dangerous hazard. These items includedoor stops, buffers, wheels and draught excluder strips.

With a combination of some of the above situations and in certain wind conditions,the lateral stability of a door may be at risk. If a roof is subject to wind uplift, thetop guide rails will deflect upwards with the roof structure to which they areattached.



December 200154545454

11.3 DOOR OPTIONS DOOR OPTIONS DOOR OPTIONS DOOR OPTIONS

There are various options which will vary depending on the site specificrequirements. Generally these are:

Option D1 Retain repair and refurbish existing doors. Maintain existingarrangement with the steel plates on the front and rear faces.Refurbishment can include provision for either:

A. Manual operationB. Automatic operation

Option D2 Provide new doors similar to existing with automatic operation.

Option D3 Do nothing (rarely suitable due to deterioration of the door).

Where there is no specific requirement to retain the door or where the opening sizemay be reduced the following may apply.

Option D4 Decommission but retain as a structural wall.

Figure 11.1 indicates this option.

Option D5 Remove existing doors and infill.

Figure 11.2 indicates this option.

In options D4 and D5 the opportunity can be taken to introducesmaller roller shutter doors or up and over industrial doors asillustrated in Figs 11.1 and 11.2.

Option D6 Remove existing doors, infill partially and provide reduced heightand/or width doors commensurate with the ability to retain accessfor aircraft involved eg. helicopter hangerage may not require fullheight access doors.

It is recommended that an option study identifies the separate alternatives of manualor automatic operation. Risk assessments of the use of existing, refurbished and newdoors should be included in the option study.

Further details of Options D1 to D6 are provided at Annex H.

It is recommended that the temporary loading conditions be considered fully whenconsidering complete removal of doors. Adverse structural consequences to roofmembers can arise in certain circumstances and these must be managed out.

11.4 DOOR INSPECTIONS DOOR INSPECTIONS DOOR INSPECTIONS DOOR INSPECTIONS

Doors require regular inspection and maintenance to prevent deterioration. Thegravel infill, if still in place, should be completely removed. They should be fullyoperational whilst ensuring that all means of access to a building remain safe.

It is known that the door plates are an integral part of the door structure. Therefore,no modifications to the door structure are to be carried out, without first carrying outa comprehensive analysis taking into account the door structural members, bracingand plating etc, and the site specific loadings.



December 2001 55555555

The door top guides, supporting brackets, door stops, bottom tracks etc, are all anintegral part of the door system, which also require regular inspection andmaintenance.

For further details and guidance, reference should be made to DE TechnicalBulletins 99/29 and 99/30, and DE Health and Safety Warning Notice 01/02.

11.5 HANGAR DOOR OUTRIGGER STRUCTURES HANGAR DOOR OUTRIGGER STRUCTURES HANGAR DOOR OUTRIGGER STRUCTURES HANGAR DOOR OUTRIGGER STRUCTURES

These are typically exposed steel latticed frames, supporting the door top guides,located on either side of the doors, to allow the doors to fully open giving full widthaccess in to the hangar.

The top door guides are usually beam or channel sections, positioned horizontally.This arrangement allows debris and water to collect in the horizontal webs. Thisarea needs to be checked for debris and corrosion. Small holes can be drilled in thewebs at regular centres, to allow surface water to drain away. Ensure that the holesare painted, or corrosion will take place.

The frame sections and the corrosion protection needs to be checked, and for anyphysical damage, at ground level, If any physical damage is found, then repairs areto be carried out, and consideration is to be given to the provision of protectionbollards around the frames.

The outrigger lattice frames are subject to high wind loads, when the doors are in theopen position, and as such, high uplift forces can be generated, and are resisted bythe foundation holding down bolts. This condition should not normally occur, as thedoors should be closed when high winds are forecast. Nevertheless, the projectingholding down bolts, and the frame base plates, which are usually located just aboveground level, are to be regularly inspected for corrosion and damage.

Repairs to corroded sections usually involve removing existing paint finishes andwelding plates or suitable sections, to achieve full section properties.

The paint finish is to be re-instated to the repair areas, or the whole of the exposedframe and door guides can be re-treated with a suitable system.

11.6 BLAST AND FRAGMENT PROTECTION BLAST AND FRAGMENT PROTECTION BLAST AND FRAGMENT PROTECTION BLAST AND FRAGMENT PROTECTION

As stated in 11.1, the cavity of the door structure was originally gravel filled toprovide this protection, which was subsequently removed. However, if there is arequirement to reinstate this protection, as part of any refurbishment, then adviceshould be sought from the ‘Protected Buildings and Weapon Effects (PBWE)’section of Defence Estates.

Contact:

Protected Buildings and Weapon EffectsDefence EstatesBlakemore DriveSutton ColdfieldWest MidlandsB75 7RL

Tel: 0121 311 3626Fax: 0121 311 3602



December 200156565656

R em ove ex is ting doorgan try o r re ta in forposs ib lerecom m iss ion ing o fdoors.

Vertica l pro filedc ladd ing to 1934hangars, p itched roo fshee ting to 1938hangars.

N ew insu lated pro filedm eta l c ladding on newsheeting rails , as in fillover doors.

H angar doors m ovedaside and perm anentlysecured in pos itionand decom m iss ioned .

N ew ro lle r shu tte r o rup and over industria ldoor.

End Elevation Existing doors fixed in position as permanent cladding

Figure Figure Figure Figure 11.1 11.1 11.1 11.1 Door Option 4. Decommissioning of hangar doors but retention as structural wall

P e rs o n n e l D o o r

V e r t ic a l p r o f ile d c la d d in g to 1 9 3 4 h a n g a rs , p itc h e d ro o f s h e e t in g to 1 9 3 8 h a n g a rs .

E x is t in g d o o rs re m o v e d a n d r e p la c e d w ith n e w in s u la te d p r o f i le d m e ta l c la d d in g o n n e w s h e e t in g ra ils .

E x is t in g r e d u n d a n t d o o r g a n t ry m a y b e re m o v e d a s o p p o s i te s id e .

N e w r o lle r s h u t te r o r u p a n d o v e r in d u s t r ia l d o o r .

End Elevation Existing doors removed and replaced with new cladding

Fig Fig Fig Fig 11.2 11.2 11.2 11.2 Door Option 5 Remove existing doors and infill.



December 2001 57575757

T op gu ide ro lle r.

C as t s tee l w hee l.

R o lled s tee l bo ttom ra il

r.c . founda tion .

S tee l p la te doo rs .

2 / 3 1 /2" x 2 1 /2" x 1 /4 "

4 / 5 " x 4 1 /2" x 18 lb /ft B S B ro lle r gu ides

Figure Figure Figure Figure 11.3 11.3 11.3 11.3 Section through top and bottom door guides



December 200158585858


December 2001 59595959

12 Roof access

1. It is MOD policy to comply with the 1974 Health & Safety at Work Act, theWorkplace (Health, Safety and Welfare) Regulations 1992, the Management ofHealth and Safety at Work Regulations 1999 and the Construction (Health, Safetyand Welfare) Regulations 1996.

2. Regulation 13 of the Workplace (Health Safety and Welfare) Regs providesguidance on falls or falling objects eg.

para (1). “So far as is reasonably practicable, suitable and effective measuresshall be taken to prevent any event specified in para (3)”.

para (3). “The events specified in this paragraph are:(a) any person falling a distance likely to cause personal

injury.(b) any person being struck by a falling object likely to

cause personal injury."

3. Access to the roof is to be determined by hazard identification and risk assessment.The risk assessments should include a consideration of the competence of thepersonnel involved, the tasks on which they are engaged and the likelihood ofslipping, falling, the presence of fragile materials, etc.

4. It is generally not economic to provide 365 days access to untrained people. It isrecommended that suitably trained/screened people are to be used for variousactivities.

(a) for routine pre planned works purposes access, is preferably restricted todaylight hours when conditions are not windy, icy or wet (wind speedto be identified in risk assessment).

(b) User requirements over and above (a) will dictate commensurate enhanced provision eg. access works and/or better calibre of

personnel.

5. The property management system under DE Specification 005 indicates thattechnical inspection are required every 2 years, and therefore, appropriate access isrequired to ensure that a meaningful visual inspection can be made of the roof.

6. External lights, antennae and lightning protection are often installed on roofs andthese may dictate more frequent inspections. The additional costs of these activitiesshould be identified at Option Study stage.

7. Work to the roofs may be identified during the technical inspections. In additionwork may be programmed on a periodic basis eg. cleaning of clear roof panels,valley gutters, outlets, etc.


12 Roof access

December 200160606060

8. Guidance on roof working is available in HSE publications.

(a) HSG 33:1998 Health and Safety in Roof Work. HSE

(b) HSG I5O: 1996 Health and Safety in Construction. HSE

9. Method of access must be recorded for each major structure and the PropertyManager must ensure that this information is kept within the Master Index and ismade available for any person needing to go on to the roof.

The “Method of access” record should be prepared either at(a) the time of need(b) the next professional appraisal(c) the time of project or works service involving a refurbishment

(eg. to meet CDM requirements).

10. Flat roofs (up to 10 degrees slope) Where there is no need to inspect perimetergutters or the perimeter from the roof, permanent means of protection need not beprovided.

11. Roofs (above 10 degrees slope) Provision is to be made for permanent protectioneg. by edge protection and/or work positioning devices or fall arrest devices.

The means of permanent protection must be commensurate with the competencesand knowledge of the personnel requiring access. For instance, if a suitable systemof body harness is required to undertake the work this dictates a level of competenceand underpinning knowledge only demonstrated by a defined class of personnel.Refer to DE Technical Bulletin 00/06 Fixed Access Ladder Systems and SRP 07Safety Rules and Procedures For Working at Height.

12. Damage can be caused to the roof surface by incorrect footwear and inappropriatesharp or heavy objects. As examples, single ply membranes can be punctured or theprotective coat to steel sheeting can be violated.

13. Warranties Installers and manufacturers warranties/guarantees can be invalidatedby people who are not made aware of specific requirements when working on roofs.A positive “no blame” culture must be developed to ensure that the location of anydamage accidentally caused is reported to the Property Manager immediately.

14. Access to the roof

Reference should be made to DE Technical Bulletin 00/06 Fixed Access LadderSystems.

In general terms the arrangements are:

Ladder Type 3 used in conjunction with Working Platforms spaced at 3 metresmaximum (used by general worker).

Ladder Type 2 in conjunction with Access Platforms spaced at 6 metres maximum(used by an authorised worker.)


12 Roof access

December 2001 61616161

Ladder Type 1 (and Rigid Rail Fall Arrest System) in conjunction with RestPlatforms spaced at 15 metres maximum (used by authorised basic climbers).

15. Access on the roof The requirements at roof level eg. provision of handrails,walkways, anchorages, will influence the decision on whether a general worker, ascreened worker or authorised climbers are required.

For option study purposes it is recommended that the Ladder Type 2 solution isadopted as a minimum. This will require two intermediate platforms to suit theheight of 14m to eaves level, plus a top platform at eaves level. If the ProjectSponsor requirement is for a Ladder Type 1 solution then this should be included atoption study stage.

16. Adverse effects of access provision Wherever possible the need for access to theroof should be minimised. Numerous additions to a roof results in an increasedaccess requirement due to a consequent additional inspection and maintenancerequirements. Provision of permanent protection to meet this need eg. by edgeprotection, work position devices or fall arrest devices and associatedfixings/anchors/eyebolts leads to an inspection requirement in itself. Unless greatattention is given to the design and workmanship, the use of fixings/anchors/eyeboltscan cause the watertightness of the roof to be impaired.


12 Roof access

December 200162626262


December 2001 63636363

13 Standards and regulations

It is Government Policy that although the Crown is exempt from the provisions of thevarious Building Acts and Regulations all construction carried out on behalf ofGovernment Departments is to comply with the substantive requirements of the relevantActs of Parliament and Statutory Instruments, and that this compliance can bedemonstrated.

13.1 BUILDING REGULATIONS BUILDING REGULATIONS BUILDING REGULATIONS BUILDING REGULATIONS

At the present time The Crown is exempt from the substantive and proceduralrequirements of the Building Regulations. However it is Government policy that wecomply with the substantive or technical requirements. Notice has been given that itis the intention of the Government to remove Crown exemption from the substantiverequirements in the near future resulting in MOD having to comply by way of lawrather than policy. The MOD has a system in place to deliver compliance with theBuilding Regulations. Details of this sytem can be found in Technical Bulletin01/26 'The Method of Operation of the MOD Building Control Compliance System'.

The regulations that apply to each project will be determined by location.

England & Wales : The Building Regulations 2000 (Statutory Instrument No2531)

Scotland : The Building Standards (Scotland) Regulations 1990 (asamended)

Northern Ireland : The Building Regulations (Northern Ireland) 1994 (asamended 1995 & 1997)

The Building Regulations are not applied retrospectively but where majorrefurbishment works are carried out to a building, the works may be considered as a'Material Alteration' requiring compliance with the Building Regulations.

An alteration is considered material for the purposes of the regulations if the work,or any part of it, would adversely affect the level of compliance in the existingbuilding of the following sections:

Part A: StructurePart B: Fire SafetyPart C: Access & Facilities for the Disabled

There is an amendment proposed to the Building Regulations (England & Wales)which suggests that Part L, Conservation of fuel and energy may be added to theabove list.

Consideration should also be given to the requirements of the DisabilityDiscrimination Act 1995 which may have some impact when it comes into full effectin 2004.



December 200164646464

Further advice on compliance with Building Regulations is available from:

DE Specialist Building Control OfficerDefence Estates CentralBlakemore DriveSutton ColdfieldWest MidlandsB75 7RL

Tel: 0121 311 3854Fax: 0121 311 3636

13.2 PLANNING AND FIRE OFFICER APPROVALSPLANNING AND FIRE OFFICER APPROVALSPLANNING AND FIRE OFFICER APPROVALSPLANNING AND FIRE OFFICER APPROVALS

Works to the hangars which significantly affect the external appearance of thebuildings, increase the volume, or raise the roof height should be notified to theLocal Planning Authority (LPA) using the Circular 18/84 Notification ofDevelopment process. The area Defence Estate Advisor should also be involvedwith any application.

Changes of use of the building may or may not require planning permission butshould be notified to the LPA for a determination. Changes of use and internallayout will usually require consultation with the Fire Prevention Officer as they arelikely to alter means of escape provisions and the fire risks of the new use may begreater or less than existing.

13.3 CROWN FIRE STANDARDSCROWN FIRE STANDARDSCROWN FIRE STANDARDSCROWN FIRE STANDARDS

It is expected that each site will be subject to a Fire Risk Assessment Methodology(FRAM) analysis to determine the minimum levels of Fire Protection provision.Crown Fire Standards and, in particular, Fire Standard E10 - “Aircraft Hangars” aremandatory for all new build hangars and they are to be applied, so far as isreasonably practicable, when major refurbishment or modernisation of hangars iscarried out. The Crown Fire Standards are not however retrospective and, where forexample, only limited renewal works items such as roof cladding are carried out,then only that element of the works is required to comply with the Standard.

It should be noted that the relevant Crown Fire Standard to be applied is determinedby the proposed use of the hangar building and not by what it was built fororiginally. Therefore, Crown Fire Standards E9 - “Vehicle Workshops and Storage,Garages and Car Parks” or E11 - “Storage Premises” may be relevant Fire Standard.

Further advice on compliance with the respective Fire Standards is available from:

Senior Fire Prevention OfficerDefence EstatesBlakemore DriveSutton ColdfieldWest MidlandsB75 7RL

Tel: 0121 311 3634Fax: 0121 311 3636



December 2001 65656565

13.4 HEALTH AND SAFETYHEALTH AND SAFETYHEALTH AND SAFETYHEALTH AND SAFETY

It is MOD policy that all works fully comply with relevant Health and Safetylegislation. The guidance provided in JSP 375 the MOD Health and SafetyHandbook should be followed.

13.4.1 The Health and Safety at Work etc. Act 1974

The main purpose of the Health and Safety at Work etc. Act is to secure the health,safety and welfare of people at work, and to protect others against risks arising outof those work activities. The Act also controls the keeping and use of explosive,highly flammable or other dangerous substances. The Act is supplemented byHealth and Safety Regulations, of which the following are particularly relevant toMT facilities:

• Workplace (Health, Safety and Welfare) Regulations 1992

• Provision and Use of Work Equipment Regulations 1998

• Manual Handling Operations Regulations 1992

• Management of Health and Safety at Work Regulations 1999

• Health and Safety (Safety Signs and Signals) Regulations 1996

13.4.2 The Construction (Design and Management) Regulations 1994(As amended by the Construction (Design & Management) AmendedRegulations 2000).These regulations do not supersede the Health and Safety at Work etc. Acts, butplace new duties upon clients, their agents, designers and contractors to take healthand safety issues into account and co-ordinate and manage them effectivelythroughout all stages of a construction project, from the inception to the completionof the work on site and subsequent operation, maintenance and repair.

The following DE Technical Bulletins should be referred to:

TB 95/23 Health and Safety CDM Regulations 1994 as applied to projects

TB 95/24 Health and Safety CDM Regulations 1994 as applied to PropertyManagement

TB 95/24 Addendum to Technical Bulletin 95/24

Further advice on compliance with the above documents is available from:

DE Health and Safety OfficerDefence EstatesBlakemore DriveSutton ColdfieldWest MidlandsB75 7RL

Tel: 0121 311 2077Fax: 0121 311 3602

13.4.3 Control of Substances Hazardous to Health Regulations 1994 (COSHH)

The aim of the Control of Substances Hazardous to Health Regulations is to provideprotection from the effects of work with substances hazardous to health. Thesesubstances range from common materials such as cement or paint, to those whichmay be present on a site, such as toxic materials in the soil or silica in masonry.



December 200166666666

13.5 PHYSICAL SECURITY PHYSICAL SECURITY PHYSICAL SECURITY PHYSICAL SECURITY

During any refurbishment project, the Project Sponsor must give consideration tophysical security.

Guidance to Project Sponsors, Property Managers and security officers on themethods of obtaining security assistance and advice for works services is given inJSP 440, Vol 1, Chapter 5.

The design of new walls should comply with the requirements of the BuildingRegulations in respect of structural stability, resistance to damp penetration andthermal performance.

The security class of the building, as well as its liability to terrorist attack, mayaffect the type and strength of glazing required in any works where windows, doorsor glazing are proposed to be replaced. DE Design and Maintenance Guide 02 -Glazing Standards for MoD Buildings subject to terrorist threat is a mandatorydocument if the building is assessed as being at risk.

13.6 ENVIRONMENTAL LEGISLATIONENVIRONMENTAL LEGISLATIONENVIRONMENTAL LEGISLATIONENVIRONMENTAL LEGISLATION

It is MOD policy to comply with the Environmental Protection Act 1990 and otherrelevant legislation. The guidance provided in JSP 418, the MOD EnvironmentalManual, should be followed.


December 2001 67676767

Annex A Record of drawings

a) CAD drawings of typical detail drawings and sketches:

Drawing No. Title

DE/H1/001/101 ‘C’ Type Hangar - Gabled (1934)GA Original Drainage

DE/H1/001/102 ‘C’ Type Hangar - Gabled (1934)Foundation Plan

DE/H1/001/103 ‘C’ Type Hangar - Gabled (1934)GA Plans and Elevations

DE/H1/001/104 ‘C’ Type Hangar - Gabled (1934)GA Steelwork Layout

DE/H1/001/105 ‘C’ Type Hangar - Gabled (1934)Main Truss ‘A’ Details

DE/H1/001/106 ‘C’ Type Hangar - Gabled (1934)Secondary Truss Details

DE/H1/001/201 ‘C Type Hangar - Hipped (1938)GA Original Drainage

DE/H1/001/202 ‘C’ Type Hangar - Hipped (1938)Foundation Plan

DE/H1/001/203 ‘C’ Type Hangar - Hipped (1938)GA Plans and Elevations

DE/H1/001/204 ‘C’ Type Hangar - Hipped (1938)GA Steelwork Layout

DE/H1/001/205 ‘C’ Type Hangar - Hipped (1938)Main Truss ‘A’ Details

DE/H1/001/206 ‘C’ Type Hangar - Hipped (1938)Secondary Truss Details



December 200168686868



December 2001 69696969


(b) Drawings held on microfiche at DE - Hangar Type: C

CatNo

MicrofilmNumber

DrawingNumber

Hangar Drawing Title

1 0344096 831/34 C: Calc for main stanchions, door trestles grantrygirders and foundations

2 0344122 832/34 C: Calc for Roof girders

3 0344097 833/34 C: Stress Diagrams for Roof and Wind girders

4 0344129 834/34 C: Load Diagrams and Calc for Roof Trusses

5 0344098 835/34 C: Calc for Wind Girders, Vertical Bracing

6 0344118 2030/34 C: Roof Trusses

7 0344119 2031/34 C: Gables Frames, Stanchions, Founds, Bracings

8 0344112 859/35 C: Timber Purlins

9 0344113 860/35 C: Horizontal Wind Girder

10 0344114 860A/35 C: Horizontal Wind Girder

11 0344121 863/35 C: Roof Trusses

12 0344094 864/35 C: Roof Girders E

13 0344095 864/35 C: Roof Girders E

14 0344123 865/35 C: Roof Girders

15 0344124 865A/35 C: Roof Girders

16 0344099 866/35 C: Vertical Bracketing

17 0344101 867/35 C: Main Stanchions

18 0344116 868/35 C: Gullerbearer and Runway Beams

19 0344111 869/35 C: Purlin Details, Deats

20 0344110 870/35 C: Top Door Guides and Canopy

21 0344105 871/35 C: Door Trestles and Box Girders

22 0344938 870/35 C: Top Door Guides and Canopy

23 03441200344105

872/35 C: Gen Arrangement

24 0344106 873/35 C: Gable Framing

25 0344115 874/35 C: Gutters Bearers

26 0344107 878/35 C: Gutters

27 0344108 880/35 C: Corner Stanchions

28 0344943 882/35 C: Elevations and Details of Steel Windows

29 0344944 882/35 C: Elevations and Details of Steel Windows

30 0344945 883/35 C: Sprocket Wheels for MSD

31 0344103 884/35 C: Hip Rafters

32 0344117 888/35 C: Rafters and Comp’d Tie Beams in Gables

33 0344109 1581/35 C: Annexes - HB Squadron

34 0344946 2100/35 C: Annexes - AC Squadron

35 0344127 3264/35 C: Concrete Construction

36 0344128 3265/35 C: Drainage


38 0344948 3267/35 C: Arrangement and Drainage

39 0344949

0344487

3268/35 C: HB Squad - Concrete Construction



December 200170707070

40 0344937 3269/35 C: HB Squad - Concrete Construction

41 0344936 3270/35 C: Light Bomber Squad - Concrete Construction

42 0344935 3272/35 C: Fighter Squad - Concrete Construction

43 0344960 4637/35 C: A T Squad - Concrete Construction

44 0344955 5069/35 C: A T Squad - Rein Concrete Design




48 0344102 265/36 C: Main Girders, Wind Girders

49 0344950 266/36 C: Gearing Rails for Gravel Filled S D

50 03449540344100

267/36 x 2 C: MSD

51 0344953 270/36 C: Found to Door Rails

* 0344953 272/36 C: Travelling Wheels

53 0344952 273/36 C: Operating Gear, Brackets and Rollers MSD

54 0344951 274/36 C: Cocking Attach, MS Rails, Timber Buff

55 0344942 275/36 C: MSD

56 0344939 709/36 C: Founds for Steel Door Rails

* 0337138 710/36 C: Founds for Stanchions and Door Trestle


59 0344959 2953/36 C: Shed Wall Reinforcement

60 0344929 2954/36 C: Rein Concrete Design

61 0344930 2956/36

61 0344125 2955/36 C: Shed Wall Rein

62 0344931 2547/36 C: Staircase Details




66 0344958 3292/36 C: Heating Pipe Ducts

67 0344498 2546/36 C: Extra Wall Rein

68 0344488 785/36 C: HB Squad - Shed Wall Rein

69 0344489 786/36 C: HB Squad - Rein Concrete Design




73 0344493 2399/36 C: HB Squad - Shed Wall Rein





78 0344481 4636/35 C: Annex: Flying T Squad - Concrete Cons

79 0344483 172/36 C: Annex: Flying - R C Wall Details



82 0344485 548/36 C: Annex: Flying - Shed Wall Rein

83 0344486 2969/36 C: Annex: A C Squad - Plan Part Annex

84 0344941 5046/36 C: A T Squad - Concrete Construction

85 0347728 5002/36 C: R C Squad - Rein for Nor Prot




89 0347732 4997/36 C: Rein in Stanchion Casing

90 0347733 4996/36 C: Rein in Wall Beams

* 0347711 2605/36 C: Concrete Construction

* 0347712 2587/37 C: Erecting Shed



December 2001 71717171

93 0347713 3363/37 C: Rein for Normal Prot

94 0347714 4750/38 C: Erecting Shed

95 0347715 6613/36 C: Erecting Shed

96 0347816 6612/36 C: Rein for Norm Protection


98 0347818 6610/36 C: Shed Wall Reinf


100 0347698 6196/36 C: Erecting Sheds

101 0347700 6195/36 C: Erecting Sheds

102 0347701 6194/36 C: Shed Wall Reinf

103 0347702 6096/36 C: Erecting Sheds

104 0347703 6095/36 C: Elevation

105 0347704 5570/36 C: Shed Wall Details

106 0347705 5569/36 C: Shed Wall Elevations

107 0347706 4990/36 C: Shed Wall Rein F T Squad

108 0347707 4989 /36 C: Rein Norm Protection

109 0347708 4988/36 C: Rein Norm Protection

110 0347709 4987/36 C: Annex: Rein Norm Prot - F T Squad

111 0347710 5573/36 C: Annex: Concrete Const - H B Squad

112 0347711 5572/36 C: Annex: Concrete Const - H B Squad

113 0347712 5571/36 C: Annex: Stanchions Encasing - H B Squad

114 0347713 5575/36 C: Annex: Staircase Details - H B Squad

115 0347714 5574/36 C: Annex: Sections to Annex Walls - H B Squad

116 0347715 5043/36 C: Annex: Elevation H B and M B Squad

117 0347716 4995/36 C: Annex: Shed Wall Rein - H B Squad

118 0347717 4994/36 C: Rein for Norm Prot - A T Squad

119 0347718 4993/36 C: Rein for Norm Prot - A T Squad



122 0347721 4986/36 C: Shed Wall Rein

123 0347723/22 4985/36 C: Rein for Norm Prot

124 0347724 4984/36 C: Rein for Norm Prot



127 0347802 63/37 C: Shed Wall Elevations

* 0347783 64/37 C: Shed Wall Details

129 0347803/784 67/37 C: Annexe Wall Details

130 0347804/785 68/37 C: Sections to Annexe Walls

131 0347805/786 69/37 C: Staircase Details

* 0347787 3787/37 CO/S: Gen Arrangement

* 034788 3788/37 CO/S: Roof Trusses

* 0347789 3789/37 CO/S: Gable Frames, Stairs, Founds

135 0347790 3790/37 CO/S: Main and Wind Girders

136 0347791 9139/38 C Asbestos: Gen Arrangements

137 0347792 9140/38 C: Founds Plan

138 0347793 9141/38 C: Founds for Stanc + Door

139 0347794 9144/38 C: Asbestos: Framing to Side Walls

140 0347796/95 9145/38 C: Framing to Side Walls End Bays

141 0347797 9146/38 C: Arrangement of Steelwork to Annexes

142 0347798 9147/38 C: Details of Steelwork to Annexes

143 0347799 9148/38 C: M.S.D

144 0347800 9149/38 C: Details of M.S.D

145 0347801 9150/38 C: Gen Arrangement Door Gearing

146 0347735 9151/38 C: Locking Attachment



December 200172727272

147 0347736 9152/38 C: Chain Wheel for MSD

148 0347737 9153/38 C: Sprocket Wheels for MSD

149 0347738 9154/38 C: Travelling Wheels for MSD

150 0347739 9155/38 C: Pins, Handles for MSD

151 0347741 9181/38 C: Foundation Plans

152 0347742 9182/38 C: Founds for Stanchions and Door Trestle

153 0347743 9185/38 C: Framing to Side Walls

154 0344104 9186/38 C: Arrangement of MSD

155 0347744 9187/38 C: Details of MSD

156 0347745 9188/38 C: Gearing, Rails for MSD

157 0347746 9189/38 C: Locking Attachment

158 0347747 9190/38 C: Operating Gear, Brackets + Rollers

159 0347748 9191/38 C: Travelling Wheels for MSD

160 0347749 9192/38 C: Steel Doors to Annexes

161 0347750 8376/38 C: Sliding and Hinged Annexes

162 0347752 2160/35 x 2 C: Perm Camber to Roof Girders

163 0347751 1524/39 C: Steel Ties and Concrete Footings for Brick Walls

164 0347753 5478/39 C: Asbestos: Gen Arrangement

* 65/37 C: Shed: Stair Encasing and Beam Details

* 66/37 C: Shed: Annex Wall Details

167 0347803 67/37 C: Shed: Annex Wall Details

168 0347804 68/37 C: Shed: Sections to Annexe Walls

169 0347786 69/37 C: Shed: Staircase Details

* 1977/37 C: Shed: Erecting Shed

* 2678/37 C: Shed: Rein Concrete

* DCES/3/660A C: Hangar: Doors

* XK1/1 C5: Proposed Alternative Designs

* XD1/1 C34: Hip Rafters



December 2001 73737373


c) Schedule of archive drawings held at DE - Type C (1934) Hangar drawings

Neg/Print DrawingNo.

Drawing Title

P 832/34 Calculations for roof girders

P 834/34 Load diagrams & calculations for roof trusses

N 1584/34 G.A.

N 2029/34 GA

P 2029/34 G.A.

N 2036/34 Annex details & section through main wall of shed

N 2040/34 Annex: G.A. & foundations

N 2774/34 Annexe plans & elevations

N 3013/34 Details of foundations for stanchions & door trestles

N 861/35 Roof trusses (2434/37)

N 862/35 Roof trusses


N 865/35 Roof girders

N 867/35 Main stanchions (2441/37)

N 872/35 G.A.

P 872/35 G.A

N 880/35 Corner stanchions (2447/37)

P 3264/35 Concrete construction (with expansion joint on RHS ofstanchions)

P 3265/35 G.A. & details of drainage inside shed

N 3266/35 Concrete construction

N 3268/35 Concrete construction - Annexe plans & elevations

P 172/36 Side Annexe - R.C. wall details

P 173/36 Side Annexe - R.C. wall details

P 275/36 Main sliding doors

P 709/36 Foundation plan & foundations for mild steel door rails

P 2955/36 R.C. design - details of shed wall reinforcement

P 5046/36 Concrete construction (14” walls) - Annexe plans & elevations

P 3012/34 Foundation plan & details of door rail foundations



December 200174747474


d) Schedule of archive drawings held at DE - Type C (1938) Hangar drawings

Neg/Print DrawingNo.

Drawing Title

N 9180/38 G.A.

N 9181/38 Foundation plan & details of door rail foundations

N 4262/39 Main stanchion topcliffe (2386/37)

N 4263/39 Roof girders A & D - Topcliffe (2387/37)

N 4264/39 Roof girders E - Topcliffe (2388/37)


N 4266/39 Roof trusses - Topcliffe (2390/37)

N 4267/39 Roof trusses - Topcliffe (2391/37)

N 4275/39 Hips -Topcliffe (2396/37)

N 9267/39 Foundation plan & door rail foundations


Annex B Change Suggestion Form

Defence EstatesDefence EstatesDefence EstatesDefence Estates Guide to World War II HangarsGuide to World War II HangarsGuide to World War II HangarsGuide to World War II Hangars

Origi

Chan

Secti

Chan

Reas

DE R

Actio

December 2001

Wind Sensitive StructuresWind Sensitive StructuresWind Sensitive StructuresWind Sensitive StructuresSpecialist ServicesSpecialist ServicesSpecialist ServicesSpecialist ServicesBlakemore DriveBlakemore DriveBlakemore DriveBlakemore DriveSutton Sutton Sutton Sutton ColdfieldColdfieldColdfieldColdfieldB75 7RLB75 7RLB75 7RLB75 7RL

Hangar Guide 03Hangar Guide 03Hangar Guide 03Hangar Guide 03Type C HangarsType C HangarsType C HangarsType C Hangars

Change Suggestion FormChange Suggestion FormChange Suggestion FormChange Suggestion Form

Date:nator:

Reference:

ge Suggestion

on: Page:

ge detail:

Continuation sheet included? Y N

on:

Continuation sheet included? Y

eview

Referen

Action D

Approv

n:

Actione

N

ce:

ate:

ed:

d:

75757575


Annex B Change Suggestion Form

December 200176767676


Annex C Hangar Notification Form

DEFENCE ESTATESDEFENCE ESTATESDEFENCE ESTATESDEFENCE ESTATES NOTIFICATION OF:NOTIFICATION OF:NOTIFICATION OF:NOTIFICATION OF:

H

MNA

T

D(e

D

P

(inPNA

T

A

FoNAD

December 2001 77777777

Wind Sensitive StructuresWind Sensitive StructuresWind Sensitive StructuresWind Sensitive StructuresSpecialist ServicesSpecialist ServicesSpecialist ServicesSpecialist ServicesBlakemore DriveBlakemore DriveBlakemore DriveBlakemore DriveSutton Sutton Sutton Sutton ColdfieldColdfieldColdfieldColdfieldB75 7RLB75 7RLB75 7RLB75 7RL

(a) HANGAR RELATED PROBLEMS(a) HANGAR RELATED PROBLEMS(a) HANGAR RELATED PROBLEMS(a) HANGAR RELATED PROBLEMS or or or or(b) WORKS ON A HANGAR BUILDING(b) WORKS ON A HANGAR BUILDING(b) WORKS ON A HANGAR BUILDING(b) WORKS ON A HANGAR BUILDING or or or or(c) EXISTENCE OF HANGAR FOR INSERTION(c) EXISTENCE OF HANGAR FOR INSERTION(c) EXISTENCE OF HANGAR FOR INSERTION(c) EXISTENCE OF HANGAR FOR INSERTION ONTO DATABASE ONTO DATABASE ONTO DATABASE ONTO DATABASE

ANGAR TYPE: Height of Hangar in number of Standard Units(ie. 2 or 3 units high)

Location of Hangar(if different from Establishment)

Building ReferenceOD Establishmentame:ddress:

el No:

Current Use of Hangar Total Estimated cost ofWorks/Project

etails of Modifications carried out to original construction:g. new roof cladding and purlins, modified hangar doors, etc)

escription of Hangar Works/Project (or description of problem)

rogramme of Works/Project

clude expected dates of main activities eg. option study, design, tender, construction, etc)roject Sponsorame:ddress:

el No:

Project SponsorName:Address:

Tel No:

Project SponsorName:Address:

Tel No:

ny Other Comments:

rm Completed By:ame:ppointment:ate:

Address:

Tel No:

DMG 00Guide to World War II Hangars03 - Type C hangar

Annex C Hangar Notification Form

December 200178787878


Annex D

December 2001 79797979

For map of the United Kingdom showing the Basic Wind Speed.See the British Standard BS CP3 CHAPTER V Part 2: 1972


Annex D

December 200180808080

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December 2001 81818181

Annex ESafe loading

Attention is drawn to the contents of TB 99/29 Hangars - Safety of Structure -Recommendations for Users During Adverse Weather Conditions.

During Snowfall. When freshly fallen snow reaches a depth of 200 mm, the PropertyManager must advise the Commanding Officer of the possible dangers and that the hangarstructure must be put under observation. If excess deflection or other signs of structuraldistress are noted by the EWC, the occupants should be ordered to evacuate the hangar.Depending upon the level of risk attached to the dangers and the value of stores or aircraftinside the hangar, the Commanding Officer must decide if their removal is imperative.

During High Winds. When high winds are forecast, the Commanding Officer must ensurethat hangar doors are kept closed. There is a risk to the safety of the structure anddamage to roof cladding. High winds for the hangars listed in this Bulletin can beconsidered to be gusts of more than 27m/s (60mph). (NB The wind speed stated is thegust speed as against a steady wind speed).

These minimum limitations apply unless there is contrary evidence based on site specificcalculations.

Where refurbishments materially change the building form, the project manager shouldprovide information on the safe operational conditions. A site specific analysis gives theopportunity to determine the actual limiting gust speed that is allowable.


Annex E Safe Loading

December 200182828282


December 2001 83838383

Annex FRoofing options & description of roofingmaterials

The various roofing options referred to in Section 7 are summarised in Fig F1.

Figure F1 Summary of roofing options (see Section 7)

BRIEF DESCRIPTIONBRIEF DESCRIPTIONBRIEF DESCRIPTIONBRIEF DESCRIPTION FULLER DESCRIPTION OF OPTION VARIANTSFULLER DESCRIPTION OF OPTION VARIANTSFULLER DESCRIPTION OF OPTION VARIANTSFULLER DESCRIPTION OF OPTION VARIANTS

OPTION R1OPTION R1OPTION R1OPTION R1 Provide new flat over-roof: using either a single plymembrane or standing-seam aluminium sheeting,including new purlins and insulation.

OPTION R1 IS THE RECOMMENDED OPTIONOPTION R1 IS THE RECOMMENDED OPTIONOPTION R1 IS THE RECOMMENDED OPTIONOPTION R1 IS THE RECOMMENDED OPTION

Option R1A - Flat roof finished in a single ply membraneOption R1A - Flat roof finished in a single ply membraneOption R1A - Flat roof finished in a single ply membraneOption R1A - Flat roof finished in a single ply membrane

Remove all existing cladding, boarding and timber purlins, but retain thesteel structure. The new roof is formed by spanning steel purlins acrossthe existing main trusses (7.62m span) and supported on steel stubcolumns of varying height to create a fall of 1 in 40 (2.5%) from thehangar centre to the sides. The single ply membrane with separationfleece overlays rigid insulation board and is fixed to an under-lyingprofiled structural liner sheet spanning across the purlins, including avapour control layer beneath the insulation. The liner sheeting should begalvanised for durability and consideration should be given for colour-coating the underside to improve the internal lighting of the hangar.

Option R1B - Flat roof finished in aluminium standing seam sheetingOption R1B - Flat roof finished in aluminium standing seam sheetingOption R1B - Flat roof finished in aluminium standing seam sheetingOption R1B - Flat roof finished in aluminium standing seam sheeting

For this option the stripping of existing finishes and provision of newpurlins is as Option R1A. The internal liner spans between the purlinswhich, unlike option R1A, is largely non-structural and only providessupport to the insulation, which has no requirement to take foot traffic.The external aluminium sheeting is supported by the purlins viaupstanding brackets. As with option R1A, a vapour control layer shouldbe provided, and the liner sheeting should be galvanised for durabilitywith consideration given for colour-coating the underside to improveinternal lighting.

OPTION R2OPTION R2OPTION R2OPTION R2 Retain existing multi-pitch roof profile: Remove existingtimber boarding, and reclad with new profiled metalsheeting, purlins and insulation.

Option R2A - Existing Option R2A - Existing Option R2A - Existing Option R2A - Existing multi-pitch profile, multi-pitch profile, multi-pitch profile, multi-pitch profile, reclad with steel sheetingreclad with steel sheetingreclad with steel sheetingreclad with steel sheetingand existing timber boarding removedand existing timber boarding removedand existing timber boarding removedand existing timber boarding removed

Remove all existing roof coverings but retain the steel structure. Recladthe existing multi-pitch profile with new built-up roof in profiled steelsheeting supported by new purlins with inner liner, vapour control layerand loose insulation.

Option R2B - Existing Option R2B - Existing Option R2B - Existing Option R2B - Existing multi-pitch profile, as Option R2A but multi-pitch profile, as Option R2A but multi-pitch profile, as Option R2A but multi-pitch profile, as Option R2A but recladrecladrecladrecladwith aluminium sheetingwith aluminium sheetingwith aluminium sheetingwith aluminium sheeting

As Option R2A removing all existing boarding etc., and retaining existingmulti-pitch roof profile, but reclad with new aluminium sheeting in lieuof steel sheeting.

Option R2C - Existing Option R2C - Existing Option R2C - Existing Option R2C - Existing multi-pitch profile, as Option 2A but multi-pitch profile, as Option 2A but multi-pitch profile, as Option 2A but multi-pitch profile, as Option 2A but reclad withreclad withreclad withreclad withcomposite sheetingcomposite sheetingcomposite sheetingcomposite sheeting

As Option R2A removing all existing boarding and retaining existingmulti-pitch roof profile, but reclad with new composite cladding in lieuof built-up system.


Annex F Roofing options & description of roofing materials

December 200184848484

BRIEF DESCRIPTIONBRIEF DESCRIPTIONBRIEF DESCRIPTIONBRIEF DESCRIPTION FULLER DESCRIPTION OF OPTION VARIANTSFULLER DESCRIPTION OF OPTION VARIANTSFULLER DESCRIPTION OF OPTION VARIANTSFULLER DESCRIPTION OF OPTION VARIANTS

OPTION R3OPTION R3OPTION R3OPTION R3 Retain existing Retain existing Retain existing Retain existing multi-pitch roof profile: As Option R2,multi-pitch roof profile: As Option R2,multi-pitch roof profile: As Option R2,multi-pitch roof profile: As Option R2,but retain and repair existing timber boarding.but retain and repair existing timber boarding.but retain and repair existing timber boarding.but retain and repair existing timber boarding.

Option R3 - Existing Option R3 - Existing Option R3 - Existing Option R3 - Existing multi-pitch profile, as Option 2 but retain andmulti-pitch profile, as Option 2 but retain andmulti-pitch profile, as Option 2 but retain andmulti-pitch profile, as Option 2 but retain andrepair existing timber boardingrepair existing timber boardingrepair existing timber boardingrepair existing timber boarding

The existing timber boarding is often found to be of good quality andcondition. In such cases, it may be retained as the inner liner. Removeexisting roof coverings down to the boarding which shall be repaired andtreated with a preservative to resist rot and insect attack and renewingany rotten or decayed timbers. Reclad with steel sheeting on newpurlins with vapour control layer and insulation.

OPTION R4OPTION R4OPTION R4OPTION R4 Retain existing Retain existing Retain existing Retain existing multi-pitch roof profile: Clean, repairmulti-pitch roof profile: Clean, repairmulti-pitch roof profile: Clean, repairmulti-pitch roof profile: Clean, repairand coat existing sheeting with a waterproofand coat existing sheeting with a waterproofand coat existing sheeting with a waterproofand coat existing sheeting with a waterproofcompound.compound.compound.compound.

POOR VALUE FOR MONEY.POOR VALUE FOR MONEY.POOR VALUE FOR MONEY.POOR VALUE FOR MONEY.

Option R4 - Repair existing sheeting and coat with a waterproofOption R4 - Repair existing sheeting and coat with a waterproofOption R4 - Repair existing sheeting and coat with a waterproofOption R4 - Repair existing sheeting and coat with a waterproofcompoundcompoundcompoundcompound

Where a defective roof needs making good for a short term, perhapsless than five years, the existing sheeting can be cleaned, repaired andcoated with a proprietary waterproof compound. Gutter repairs may alsobe necessary.

Figure F2 illustrates how various roofing materials may be applied to the different roofingoptions (Sect 7.5).

Figure F2 Application of roofing materials to roofing options

OPTIONOPTIONOPTIONOPTION1111




MATERIALMATERIALMATERIALMATERIAL FLATOVER-ROOF

MULTI-PITCH PROFILE

RemoveRemoveRemoveRemoveexistingexistingexistingexistingtimbertimbertimbertimber

Retain &Retain &Retain &Retain &repairrepairrepairrepair

existingexistingexistingexistingtimbertimbertimbertimber

Retain &Retain &Retain &Retain &repairrepairrepairrepair

existingexistingexistingexistingsheetingsheetingsheetingsheeting

A Single ply membrane ✓ ✓ ✓

B Standing seam concealed-fix Aluminiumsheeting

✓

C Traditional profiled steel sheeting ✓ ✓

D Traditional profiled aluminium sheeting ✓ ✓

E Composite sheeting ✓ ✓

F Fibre cement sheeting ✓

G Coat with waterproof compound ✓

The recommended solution is to adopt the flat roof options using either single ply orstanding seam concealed-fix Aluminium sheeting. All the material options androofing concepts are described and discussed below.



December 2001 85858585

Description of roofing materials

Material A: Single ply membrane

The single ply membrane can be laid at minimal falls and is also suitable for pitchedroofs. It is laid over rigid insulation board and fixed to an underlying profiled structuralliner sheet spanning across the purlins. A separation fleece may be required to physicallyisolate the membrane from what may be chemically incompatible insulation board.Insulation boarding must be sufficiently robust to allow foot traffic for maintenanceaccess and this trafficking must be designed for.

In addition, a vapour control layer is normally provided beneath the insulation to preventmigration of water vapour. Otherwise such vapour can condense on the underside of thecooler membrane and be retained by the insulation which should be kept dry. Theresulting local dampness reduces the effectiveness of the insulation and also may initiatecorrosion of the fixings and liner. The liner sheeting should be galvanised for durabilityand may be suitably coated to improve brightness of the internal working environment.

Mechanically attached single ply membranes are laid in rolls and secured to the substrateby either individual fixing plates placed along one edge or linear bars secured over theroof membrane. Fixings centres must be determined by the need to resist uplift load dueto wind in accordance with British Standards. Adjoining rolls are overlapped, coveringthe fixings in edge fastened systems, and jointed by either hot air welding or chemicallybonded solvent welding.

Adhered roofing systems are laid in rolls secured to a suitable substrate with themanufacturers recommended adhesive. Adjoining rolls are overlapped and jointed byeither hot air welding or chemically bonded solvent welding.

Guarantees are available for single ply membranes. The manufacturers' recommendationand the conditions of any guarantee should be followed.

A major advantage of the single ply membrane is that no fixings or sealants are exposedto the external hostile environment, and material specifications are available for goodtear-resistance, durability and dimensional stability.

Material B: Standing seam conceal-fix aluminium system

The aluminium sheeting is supported by upstanding brackets which either sit on thepurlins or on a structural liner, the latter normally being more expensive.

The internal liner, spanning between the purlins, is usually non-structural as it only needsto support the insulation, which has no requirement to take foot traffic and so need not berigid. As with material A, a vapour control layer should be provided between the linerand the insulation. The liner sheeting is either in aluminium or galvanised steel and againas with material A, its underside may be colour-coated to improve the internal lightingaspect.

Aluminium has a coefficient of thermal expansion twice that of steel so care is necessaryin design and installation to ensure that there is adequate provision for thermal movementof aluminium sheets. In addition, if using stainless steel fixings with aluminium sheets onsteel purlins, care is needed to build in precautions against bimetallic corrosion. Isolationtapes and washers should be used where necessary, making use of manufacturers'recommendations.

The upstanding brackets, fixed through the liner, are placed on each purlin at centres tosuit the width of the standing seam sheets. Sheets are laid in sequence with one edge ofeach sheet overlapping the edge of an adjacent sheet, and are then mechanically crimpedtogether.



December 200186868686

Aluminium sheeting may be coated for cosmetic purposes, corrosion protection is notrequired. Aluminium is not as hard as steel and so is susceptible to local damage andwithin limits this is not serious. Aluminium is still harder than the protective coatingsapplied to steel, and when scratched, the oxidation process is of a self-protective nature,unlike steel. Although the coating of aluminium sheeting does not prolong its lifespansignificantly, uncoated mill-finish aluminium can be highly reflective and requires coatingto dull this effect.

Guarantees are available for standing seam aluminium systems. Manufacturers'recommendations and the conditions of any guarantee should be followed. For optionstudy purposes the period for repaint in years should be considered (refer to BS 5427 :Part 1 : 1996).

As with material A, a major advantage of this option is that no fixings or sealants areexposed to the external hostile environment. The density of aluminium is also nearly athird that of steel and so provides a lightweight roof. This makes it easier to handle, cutand drill than steel, making installation and repair of an aluminium roof a quicker process.Because of its relatively stable nature, aluminium has good economical recyclingproperties.

Material C: Traditional profiled steel sheeting

This option is not suitable for the flat roof concept, as the recommended roof pitch is inthe order of 15°. The built-up roof comprises high quality organically-coated, profiledsteel sheeting with loose insulation on inner liner trays, all supported by purlins. If theexisting timber purlins and boarding are retained, spacers will be required fixed throughthe boarding into the timber purlins beneath, but insulation would be supported by theboarding in lieu of liner trays.

The coating is necessary to protect the steel from corroding which is likely to be initiatedby damage. The steel sheet should be pre-galvanised and it is then essential that a goodquality "organic" coating is specified to both the top and underside of the steel sheet. Anewly installed steel roof cannot be assumed to be damage-free, due to possible carelessworkmanship "building-in" potential corrosion from day one. The deliberate cutting anddrilling needed to fix the roof sheets and accidental damage requires additional protectivetreatment of the exposed steel. This slows the fixing process down but unless all exposedsteel is effectively treated rusting arises. Aluminium does not require the same attentionto detail.

The durability of steel sheeted built-up roofs depends heavily on the quality ofworkmanship and exposure to the weather during installation. Any moisture or rainingressing the insulation is rarely removed before completion. The resulting localdampness and possible saturated insulation material reduces the effectiveness of theinsulation material and creates an ideal environment to initiate corrosion of the fixings,the liner and the underside of the steel sheet.

The durability of the roof is also dependent on the components making up the roofsystem. The fixings, sealants and cut edges of sheets are usually the elements thatdeteriorate first and it is these that determine its useful life. Stainless steel fixings areelectrochemically not compatible with steel, therefore, fixings for steel roofs are normallygalvanised or sheradised but are still less durable than stainless steel. Stainless steelfixings are closer in compatibility with aluminium sheeting. Periodic repair ofcomponents such as sealants is not practical or cost-effective.

Guarantees are available for coated steel sheeting. Manufacturer’s recommendations andthe condition of any guarantee should be followed. Steel sheeting is particularly prone tocorrosion resulting from damage, installation defects, unseen damage, or by not followingthe manufacturers' recommendations.For option study purposes, for the functional life period and the external environment, theperiod for repaint should be considered, (refer to BS 5427 : Part 1 : 1996).



December 2001 87878787

Coated steel roofing needs to be inspected annually to check for damage or at otherdefined periods specified under warranty/guarantee. Due to their susceptibility tocorrosion resulting from damage to the coating, it is important that inspections are carriedout regularly. The underlying steel is prone to rapid corrosion if damage is leftundetected.

Material D: Traditional profiled aluminium sheeting

The make up of this roof system is similar to material C, except that the sheeting is inaluminium. It is a built-up roof comprising profiled aluminium sheeting with looseinsulation on inner liner trays, all supported by new purlins. Again, the existing timberpurlins and boarding may be retained, and the option is not suitable for the flat roofconcept because of the nature of the system and the need for sealants. The minimumrecommended roof pitch is typically 15°.

Aluminium sheeting is expensive initially, however, it is more durable and requires lessmaintenance, and is said to be more cost effective in the long term. Aluminium is notprone to corrosion and damage tends to self-heal. Coatings are required for cosmeticreasons only. Advantages referred to for standing seam aluminium also apply here,except that the durability of the whole system also relies on the fixings and sealants used.Care is needed in specifying ancillary components, to ensure the envisaged lifespanapplies to all parts of the system. Periodic repair of components such as sealants is notpractical or cost-effective.

Material E: Composite sheeting

Composite sheeting comprises a series of pre-assembled panels bonding two profiledmetal skins around a core of insulation in a sandwich construction. The sheeting can bein either coated steel or aluminium. Although normally more expensive initially, thesystem usually provides a better quality product than the equivalent built-up system. Asthe internal and external sheets are separated by the insulation, cold bridging is minimal,which reduces the risk of soffit condensation. Factory assembly gives scope for betterquality control measures hence the risk of water ingress to the insulation is reduced.

The drawbacks are that the multi-pitch nature of the Type C roof dictates short lengths ofcut panel. The system still requires sealants and fixings along the joints and, because ofits composite nature, damage is both more expensive to repair. Treatment of steel panelcut edges is still needed, and regular inspections are required to ensure the continuedeffectiveness of the coating is maintained. Composite panels are heavier and moredifficult to handle, and their rigidity also offers little flexibility to accommodateirregularities found in old roof structures. The system is unsuitable for the flat roofconcept due to the minimum roof pitch requirements associated with the flat roof.

The expected lifespan depends on the materials used.



December 200188888888

Material F: Fibre cement sheeting

This option is a similar system to the original asbestos cement roof sheeting, in terms ofappearance. The ability of the sheeting to resist bending, relies on the tensileperformance of the fibres. Although the fibres have an adequate tensile yield stress, theystretch excessively under load and the cement cracks. When laid on Type C roofs, fibre-cement sheeting, therefore, has limited capability to accommodate irregularities found inthe roof structure and any movements.

This material has good breathability and reduces condensation. Additional insulationshould be provided for which existing timber boarding or new liner trays and purlinswould be needed to support the insulation if placed within the new roof construction.

Material G: Coat with waterproof compound

Where a defective roof needs making good for a short term of less than five years, aproprietary overlay or patch repair system may be considered. The existing sheetingrequires thorough prior cleaning. Provision should be made for the collection, retentionand disposal of any asbestos fibres loosened in the cleaning process. Proprietary cleaningsystems are available, which use special brushes pre-cut to the profile of the existing roof.

The existing roof needs a thorough check for integrity of fixings, cracked sheets orevidence of leaking. Repairs are required before the cleaning proceeds. After cleaning, afungicidal wash is required to kill off and remove lichen spores embedded in the roofsurface. After completing all preparation work, a quality waterproof and vapour-permeable coating may be applied to the existing sheets.

Other materials

Lead, copper, zinc or slate roofing materials are available, however it is not consideredthat these materials are appropriate for the large areas involved.

Period to repaint

For option study purposes, the period to repaint in years should be considered within thecontext of the type of external environment, and the guidance given within Annex D, ofBS:5427:Part 1:1996.

GUIDANCE PUBLICATIONSGUIDANCE PUBLICATIONSGUIDANCE PUBLICATIONSGUIDANCE PUBLICATIONS

• BS 5427:Code of Practice for the Use of Profiled Sheet for Roof and Wall Claddingon Buildings. Part 1:Design

• Profiled Sheet Roofing and Cladding : A Guide to Good Practice, NationalFederation of Roofing Contractors. Third Edition:1999

• Technical Paper No 5:Metal Wall Cladding Detailing Guide, MCRMA• Technical Paper No 6:Profiled Metal Roofing Design Guide, MCRMA• Technical Paper No 9:Composite Roof and Wall Design Guide, MCRMA• BRE Digest 372:Flat Roof Design: Waterproof Membranes, BRE• CIRIA Book 15:Flat Roofing Design and Good Practice, CIRIA• The Single Ply Roofing Association - Code of Practice• Guidance of Design Criteria For Single Ply Roofing Membranes• Durability of Cladding:A State of the Art Report, W S Atkins & Others• Coated Metal Roofing & Cladding:Oliver Albon & Garner, Thomas Telford Ltd.


December 2001 89898989

Annex GWindow refurbishment options andtypical window drawings

The advantages and disadvantages of the various window options (sect 9) are:

OPTIONOPTIONOPTIONOPTION ADVANTAGESADVANTAGESADVANTAGESADVANTAGES DISADVANTAGESDISADVANTAGESDISADVANTAGESDISADVANTAGES COMMENTCOMMENTCOMMENTCOMMENT

OPTION W1OPTION W1OPTION W1OPTION W1 Remove existing andprovide solid infill, oroverclad with suitableinsulated opaquecladding.

Savings in heat losses. Full artificiallighting is normally required forwinter or night working.

Removes natural light provision,and is therefore not appropriatewhen natural light is specificallyidentified in the statement ofrequirement.

Practical and economical,particularly in the long term.DE RECOMMENDEDDE RECOMMENDEDDE RECOMMENDEDDE RECOMMENDEDOPTIONOPTIONOPTIONOPTION

OPTION W2OPTION W2OPTION W2OPTION W2 Remove existing andreplace with translucentwall cladding or multi-wall polycarbonatesheeting with suitablelight diffusion, thermaland durabilitycharacteristics.

Diffusive properties of translucentcladding or polycarbonate sheetingprovide improved lightingconditions, more suitable to theworking environment required inhangar type buildings. Sympathiseswith the preferred solution tooverclad the walls, and translucentsheeting can be in the same profileas the main wall cladding.

Additional costs of windowprovision.

Practical and economicalsolution when the SOR dictatesnatural lighting.

OPTION W3OPTION W3OPTION W3OPTION W3 Remove existing windowand replace with doubleglazed units inappearance similar toexisting.

Improved appearance. Expensive initially. Diffused glassremoves clear views.

Hangar type buildings do notneed high specification doubleglazed windows, which aremore suited to office buildings.

OPTION W4OPTION W4OPTION W4OPTION W4 Retain existing windowsif condition permits, andrepair. Strengthen ifrequired.

Full repair costs may not beapparent until work starts.Maintenance is high. Corrosionaccelerated by the condensationproblems. May be a need tostrengthen the windows. Heatlosses are not reduced. Diffusedand contrasting patterns of lightwith varying intensity is not ideal forhangar-type work.

Frames are usually corroded,particularly the bottom cill.


Annex G Window refurbishment options and typical window drawings

December 200190909090

Typical drawings are given to illustrate the typical solutions. However, it shallremain the responsibility of the contractor to provide as constructed solutions whichare fit for purpose.

VERTICAL SECTION

Sheradized steel fixings.

Flashing

Window head

Continuous 90x90x8 ms galv. angle bolted to top of window.

90x90x8 ms galv. angle bolted to vertical members.

Continuous 90x90x8 ms galv. angle bolted to bottom of window.

Clear triple wall polycarbonate sheeting fixed in accordance with the manufacturer's instructions.

HORIZONTAL SECTION

89x89 rsj (min) or 2/90x90 ms angles at expansion joints. Actual sizes of vertical supports to suit height of windows and hangar location.

Manufacturer's end plate

90x90x8 galvanised ms angles

Option W2Option W2Option W2Option W2 - Vertical section thro' window showing New Polycarbonate Sheeting

Option W2Option W2Option W2Option W2 - Horizontal section thro' window showing New Polycarbonate Sheeting



December 2001 91919191

Option W2Option W2Option W2Option W2 - Vertical section through window showing new translucent sheeting



92929292

Option Option Option Option W4W4W4W4 Vertical section showing strengthening of existing Profilit glazing


December 2001 93939393

Annex HDoor refurbishment options

Any option should have regard to the extant information.

TB99/29 Safety of Structure - Recommendations for users during adverse weather conditions.

TB99/30 Inspection, maintenance, adjustment and use of large sliding and folding doors.

TB99/31 Guidance on works during hangar refurbishment and hangar identification.

TB97/40 H&S - Fixed electrical power distribution for aircraft hangars and hardenedaircraft shelters.

HSWN 01/02 Inspection of hangar doors, Door Top Guides - Type C hangars.

HSWN 95/07 Inspection of hangar doors.

The options below draw out some of the issues involved. A detailed site specific analysisis required at each site.


Annex H Door refurbishment options

94949494


OPTION D1OPTION D1OPTION D1OPTION D1 Refurbish existing doors.

A. Manual operation Operation of doors will be greatlyimproved due to:

- Reduced weight;- New running gear;- Manual brake;- Continuous and adjustable bottom track;- Removal of general debris via catchpits to prevent jamming;- Removal of surface water via catchpits to reduce incidence of ice formation.

Full maintenance access to allrunning and operating gear.Maximum number of open doorconfigurations maintained.Maximum door width and heightmaintained.Maximum flexibility for future usemaintained.Heat loss minimised.Lowest cost of all options.Minimal running costs.Reduced maintenance costs.

Reliance on manual operation.Braking and crank handle"snatching" significantly reduced butnot entirely eliminated.

B. Automatic operation Operation of doors will be greatlyimproved (as Option D1A)Full electric operation with manualoverride provided.Maximum door height and widthmaintained.Flexibility for future use maintained.Heat loss reduced.Reduced maintenance costs.

Initial cost is prohibitive whencompared with option D1A.Maintenance costs are likely to behigher than option D2 where totallynew doors are provided.Current operational flexibility interms of open door configurationsreduced due to door linkage.

In order for this option toachieve the same low level ofmaintenance as option D2 ahigh emphasis will be requiredwhen assessing theacceptability for re-use orotherwise of the existing doorcomponents. Goodcompatibility will need to beachieved between existing andnew components to ensure thatall elements achieve therequired operational design life.

OPTION D2OPTION D2OPTION D2OPTION D2 Provide new doorssimilar to existing withautomatic operation

All door components are new.Ease of operation.Full maintenance access to allrunning and operating gear.Maximum door width and heightmaintained.Heat loss minimised.Maintenance costs are likely to beless than option D1B.Increased certainty of achievingrequired minimum design life whencompared to Option D1B.

Highest initial cost.Potential for icing-up of bottomtracks remains.

OPTION D3OPTION D3OPTION D3OPTION D3 Do nothing 1) long term risks to H&S of operatives and damage to equipment due to collapse of doors2) ever increasing maintenance costs.3) increased risk of disruption to hangar operations

Not recommended.



December 2001 95959595


OPTION D4OPTION D4OPTION D4OPTION D4 Decommission but retainas a structural wall

Maintenance of doors and runninggear reduced.Heat loss minimised.Low cost option.Insulation linings can be fixed to theinside face.

Re - Commissioning will be verydifficult, and full inspection will berequired.Doors must be in good structuralconditions.

OPTION D5OPTION D5OPTION D5OPTION D5 Remove existing doorsand infill

End walls can be fully insulated.No external maintenance.Existing good condition doors canbe used on other structures.

High initial costs.Not readily amended back to fullhangar doors.

OPTION D6OPTION D6OPTION D6OPTION D6 Remove existing door,infill partially and providereduced height and/orwidth doors

Lowest initial cost for electricallyoperated doors.Lower maintenance costs than someoptionsEase of operationIcing-up of bottom tracks can beeliminated.Addresses all Health and Safetyissues attached to manualoperation.Least heat loss of all options.Door openings optimised for use byvehicles, helicopters etc.

Minor reduction in flexibility forfuture use by larger aircraft.This option will preclude the use ofthe hangars aircraft as identified asbeing too wide or too tall.Reduction in long term flexibility.

To lessen the effect of any longterm loss of flexibility, it wouldbe prudent to retain the topguides and outrigger framesunder this option. This wouldpermit future re-installation ofdoors with the maximum clearopening if required.

Note:

The methodology given is illustrative of the items which may be required. This is givenas an indication of the requirement. Each site will require a specific design.



December 200196969696


December 2001 97979797

Annex ICost comparisons

No option for a solution can be given full consideration without some idea of costimplications. Technical solutions on their own do not carry any merit unless they can beproved to be economically viable.

Budget cost estimates are, therefore, given in this chapter for the basic work items inconnection with a typical Type C hangar, roof refurbishment. All costs are baseestimates, in that they are ‘raw’ costs without inclusion of risk additions, preliminaries,VAT or professional fees. A site specific investment appraisal of the various optionsshould take all such factors into account.

All estimates will require validation for a particular project and updating to current pricelevels. They provide a rough guide for budgeting and comparison purposes.

If for security reasons a dado wall is built around the perimeter of the building, then extraover costs will be incurred.

The costs for a new build hangar are not provided. It is unlikely that the ProjectSponsor’s requirement would be for the same footprint or height of hangar. Experienceindicates that a rigorous approach to determination of space requirement dictates asmaller structure with commensurate lower costs.

For comparison purposes within the Option Study it will, therefore, be necessary to obtaina Statement of Requirement which provides the space requirement.

If a green field site is chosen, the cost of site preparation and laying new services willneed to be included, together with provision of a ground slab.

The costs for refurbishment are less than a new build hangar of the same size. However, anew hangar can be designed to present day operational needs, normally with reducedmaintenance and running costs. Whole life costs of the different options should be takeninto account in an investment appraisal.

The DE view is that refurbished Type C hangars represent the best option for the client,subject to their being a defined need for the extant hangarage space.


Annex I Cost comparisons

December 200198989898

COST ESTIMATES FOR ROOF REFURBISHMENT – TYPE C 1938 COST ESTIMATES FOR ROOF REFURBISHMENT – TYPE C 1938 COST ESTIMATES FOR ROOF REFURBISHMENT – TYPE C 1938 COST ESTIMATES FOR ROOF REFURBISHMENT – TYPE C 1938

Based on estimates at the first quarter 2000 prices

OPTIOOPTIOOPTIOOPTIONNNN

DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION VARIANTVARIANTVARIANTVARIANT ITEMITEMITEMITEM COST £COST £COST £COST £

R1R1R1R1 Provide new mansard over roof,remove existing roof coveringincluding timber boarding

A – Clad with single ply membrane Strip

Work to existing

New roof construction

New parapet gutters

35050

25080

168260

15920

Total Option R1ATotal Option R1ATotal Option R1ATotal Option R1A 244310244310244310244310

RECOMMENDED OPTIONRECOMMENDED OPTIONRECOMMENDED OPTIONRECOMMENDED OPTION B – – – – Clad with aluminium standing seam Strip

Work to existing


New parapet gutters

35050

25080

196460

15920

Total Option R1BTotal Option R1BTotal Option R1BTotal Option R1B 272510272510272510272510

R2R2R2R2 Retain existing valley profile, removeexisting roof covering includingtimber boarding

A – – – – Clad with profiled steel sheeting Strip

Work to existing


New valley/parapet gutters

35050

8360

130560

56250


B - Clad with profiled aluminium sheeting Strip

Work to existing



35050

8360

165240

56250


C – – – – Clad with composite steel sheeting Strip

Work to existing



35050

8360

160000

56250

Total Option R2CTotal Option R2CTotal Option R2CTotal Option R2C 322020322020322020322020

R3R3R3R3 Retain existing valley profile, removeexisting roof covering, retain andrepair timber boarding

A – – – – Clad with profiled steel sheeting Strip

Work to existing



19750

21570

99960

56250


B – – – – Clad with profiled aluminiumsheeting

Strip

Work to existing



19750

21570

129540

56250


R4R4R4R4 Repair and coat original sheetingwith a waterproof compound

Not recommended.Not recommended.Not recommended.Not recommended.Poor value for moneyPoor value for moneyPoor value for moneyPoor value for money Total Option R4 Total Option R4 Total Option R4 Total Option R4 ApproxApproxApproxApprox

200000200000200000200000

Note:

The above figures are subject to confirmation and are based on a C Type hangar with12 bays giving a footprint of 4180 m2 on PLAN (excluding annex roofs).


December 2001 99999999

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2. Appraisal of Existing Iron and Steel Structures, Publication 138, 1997. SteelConstruction Institute. ISBN 1859420095.

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9. BS 5628: Part 1: 1992. Code of Practice for Use of Masonry. British StandardsInstitution.

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14. BS 6651 : 1999. Code of Practice for Protection of Structures Against Lightning.British Standards Institutions.

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23. BRE Information Paper 19/81: 1981. Assessment of Hard Body ImpactResistance of External Walls. Building Research Establishment.

24. Technical Instruction CE: 104: 1986. Appraisal of Existing and Design of NewRunway and Lifting Beams. Property Services Agency.

25. Corrosion Damaged Concrete: Assessment and Repair: 1987. By Pullar-Strecker,P Butterworths. ISBN 0408025565.

26. Health and Safety at Work, etc, Act: 1974. HMSO. ISBN 0105437743.

27. The Workplace (Health, Safety and Welfare) Regulations: 1992. StatutoryInstrument No 3004. HMSO. ISBN 0110258045.

28. The Management of Health and Safety at Work Regulations: 1999. StatutoryInstrument No 3242. HMSO. ISBN 0110856252.

29. The Construction (Health, Safety and Welfare) Regulations: 1996. StatutoryInstrument No 1592. HMSO. ISBN 0110359046.

30. Health and Safety (Guidance) HSG 33: 1998. Health and Safety in Roof Work.HSE. ISBN 0717614255.

31. Health and Safety (Guidance) HSG 150: 1996. Health and Safety in Construction.HSE. ISBN 0717611434.

32. The Provision and Use of Work Equipment Regulations: 1998. StatutoryInstrument No 2306. HMSO. ISBN 0110795997.

33. Manual Handling Operations Regulations: 1992.Statutory Instrument No 2793. HMSO. ISBN 0110259203.

34. Health and Safety (Safety Signs and Signals) Regulations: 1996. StatutoryInstrument No 341. HMSO. ISBN 011054093X.

35. Construction (Design and Management) Regulations: 1994 (as amended by theConstruction (Design and Management) Amended Regulations 2000)Statutory Instrument No 3140. HMSO. ISBN 0110438450.

36. Control of Substances Hazardous to Health (COSHH) Regulations: 1999.Statutory Instrument No 437. HMSO. ISBN 0110820878.

37. The Building Regulations: 2000Statutory Instrument No 2531. HMSO. ISBN 0110998979.

38. The Building Standards (Scotland) Regulations: 1990.Statutory Instrument No 2179. HMSO. ISBN 0110051793.


References

December 2001 101101101101

39. The Building Regulations (Northern Ireland): 1994.Statutory Rule No 243. HMSO. ISBN 0337912432.

40. Environmental Protection Act: 1990. HMSO. ISBN 0105443905.

41. Crown Fire Standards: 1998.

Crown Fire Standard: D6. July 1998. Fire Alarm Systems - AutomaticallyOperated.

Crown Fire Standard: E4. July 1998. Office Buildings.

Crown Fire Standard: E9. July 1998. Vehicle Workshops and Storage, Garagesand Car Parks.

Crown Fire Standard: E10. July 1998. Aircraft Hangars.

Crown Fire Standard: E11. July 1998. Storage Premises.

42. Department of the Environment: 1995. Standard Fire Precautions for ContractorsEngaged on Crown works. HMSO. ISBN 0117530948.

43. Defence Estates. Property Management of the Defence Estate - DEO(W)Specification 005 Issue 003, Incorporating Amendment 1, dated 31/10/1996.

44. Joint Services Publication 315. 3rd Edition: 1999.Services Accommodation Code. Ministry of Defence.

45. Joint Services Publication 318A. 2nd Edition: 1996.Military Air Traffic Services. (Chapter 23). Ministry of Defence.

46. Joint Services Publication 375. 3rd Edition: 1995.MOD Health and Safety Handbook. Ministry of Defence.

47. Joint Services Publication 418: 1996.Environmental Manual. Ministry of Defence.

48. Joint Services Publication 440. Volumes 1, 2 and 3.Defence Manual of Security. Ministry of Defence.

49. Joint Services Publication 455: 1997.Military Aerodromes Construction and Safeguarding Criteria. Ministry ofDefence.

50. DEO(W) Specification 033: 1996. Pavement Quality Concrete for Airfields. TSO.ISBN 0117724769.

51. DEO(W) Specification 035: 1996. Concrete Block Paving for Airfields. TSO.ISBN 0117724912.

52. DWS Functional Standard 06: 1994. Guide to Airfield Pavement Maintenance.HMSO. ISBN 011772730X.

53. Design and Maintenance Guide 02: 1996. Glazing Standards for MOD BuildingsSubject to Terrorist Threat. Defence Estates.

54. Design and Maintenance Guide 13: 1998. Mechanical Transport Facilities.Defence Estates. HMSO. ISBN 0117728748.

55. Design and Maintenance Guide 20: 1999. The Heating of Large Spaces. DefenceEstates. HMSO. ISBN 0117729221.


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December 2001102102102102

56. Technical Bulletin 97/40: 1997. Health and Safety - Fixed Electrical PowerDistribution for Aircraft Hangars and Hardened Aircraft Shelters. DefenceEstates.

57. Technical Bulletin 95/23: 1995. Health and Safety CDM Regulations 1994 asApplied to Projects. Defence Estates.

58. Technical Bulletin 95/24: 1995. Health and Safety CDM Regulations 1994 asApplied to Property Management. Defence Estates.

59. Technical Bulletin 95/24; 1995. Addendum to Technical Bulletin 95/24. DefenceEstates.

60. Technical Bulletin 99/29: 1999. Safety of Structure - Recommendations for UsersDuring Adverse Weather Conditions. Defence Estates.

61. Technical Bulletin 99/30: 1999. Hangars and Industrial Buildings - Inspection,Maintenance, Adjustment and Use of Large Sliding and Folding Doors. DefenceEstates.

62. Technical Bulletin 99/31: 1999. Hangars - Guidance on Works during HangarRefurbishment. Defence Estates.

63. Technical Bulletin 00/06: 2000. Fixed Access Ladder Systems.Defence Estates.

64. Technical Bulletin 01/26: 2001. The Method of Operation of the MOD BuildingControl Compliance System. Defence Estates.

65. Health and Safety Warning Notice 95/07: 1995. Inspection of Hangar Doors.Defence Estates.

66. Health and Safety Warning Notice 01/02: 2001. Inspection of Hangar Doors,Door Top Guides. Type C Hangars. Defence Estates.

67. Safety Rules and Procedures. SRP 07: Procedures for Working at Height. DefenceEstates. (To be issued in due course).

68. AP 113A - 0201 - 1. Earthing of Aircraft and Ground Support Equipment.Defence Estates.

69. AP 100D - 20. Precautions Against Electric Shock in Electric Hazard Areas ofElectric and Electronic Facilities. Defence Estates.

70. Other Relevant AP's, (eg. AP 100B - 01). Defence Estates.

71. Various Other AGL Requirements / Standards Such as for Exterior Lighting toHangars in Vicinity of Airfields. eg. Drawing No CU (M&E) 0266. DefenceEstates.

72. Profiled Sheet Roofing and Cladding: A Guide to Good Practice: Third Edition1999. E & FN Spon. ISBN 0419239405.

73. Durability of Cladding: A State of the Art Report, WS Atkins. Thomas Telford.ISBN 0727720120.

74. Coated Metal Roofing and Cladding: Oliver, Albon and Garner. Thomas Telford.ISBN 072772620X.

75. Flat Roof Design and Good Practice: Book 15. CIRIA. ISBN 0860173453.


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December 2001 103103103103

76. The Single Ply Roofing Association:Code of practice. (Soon to become a British Standard).Guide on Design Criteria for Single Ply Roofing Membranes. (Under revision).Product Sheets 1 to 6. (Soon to be incorporated into design guide).

Further information is available from:The Single Ply Roofing AssociationThe Building Centre26 Store StLondon WC1E 7BTTel: 0115 914 4445Fax: 0115 974 9827.

77. The Metal Cladding and Roofing Manufacturers Association:Technical Paper No 5: Metal Wall Cladding Detailing Guide.Technical Paper No 6: Profiled Metal Roofing Design Guide.Technical Paper No 9: Composite Roof and Wall Cladding Panel Design Guide.

Further information is available from:The Metal Cladding and Roofing Manufacturers Association18 Mere Farm RoadPrentonWirralCheshire CH43 9TTTel: 0151 652 3846Fax: 0151 653 4080.

Prepared by: Wind Sensitive StructuresSpecialist ServicesDecember 2001

Defence EstatesBlakemore DriveSutton ColdfieldWest MidlandsB75 7RL

Tel: 0121 311 3789Fax: 0121 311 3636Sutton Coldfield Mil Extn (9) 4421

Documents

DMG 24. Guide to World War II Hangars. 03 - Type C Hnagarswebarchive.nationalarchives.gov.uk/20121026065214/ · Guide to World War II Hangars 03 - Type C Hangars December 2001 v Abbreviations