Type of assignment: 5th Semester Specific Project Title of your education: Constructing Architect

Author full name: Spas Penchev Vasilev Name of your Consultant: Mihoko Brethvad

Name of Institution – VIA University College, Aarhus, Denmark Date of handed-in the report: 5th of November 2012

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TITLE SHEET

TITEL OF THE REPORT: Renovating apartment buildings: The collar tie roof.

SUPERVISOR: Mihoko Brethvad

AUTHOR: Spas Vasilev

DATE/SIGNATURE: 05.11. 2012

STUDENT IDENTITY NUMBER: 178738

NUMBER OF COPIES:

NUMBER OF PAGES (2400 characters per page):

GENERAL INFORMATION: All rights reserved – no part of this publication may be

reproduced without the prior permission of the author.

NOTE: This report was compiled as part of the Constructing

Architect education – every responsibility concerning guidance,

instructions or conclusions is hereby renounced.

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Table of Contents INTRODUCTION ............................................................................................................................. 4

COMMON INFORAMTION ............................................................................................................ 5

Building traditions ..................................................................................................................... 5

Roof forms .................................................................................................................................... 5

Collar tie roof .............................................................................................................................. 6

The Rafter Construction ...................................................................................................... 6

Roof Eaves ............................................................................................................................... 7

Roof-Joists ................................................................................................................................ 7

Roof Claddings and Roof Flashing .................................................................................. 8

Insulation .................................................................................................................................. 8

Roofing ...................................................................................................................................... 8

EVALUATION OF THE BUILDING ............................................................................................. 9

DIRECTION - How to solve the problems and renovate? ............................................ 10

Vapor barrier ............................................................................................................................. 10

Flashing ....................................................................................................................................... 13

Straightening ............................................................................................................................ 14

Demolition .................................................................................................................................. 15

Damage from fungus, rot and insects............................................................................. 16

Roofing ........................................................................................................................................ 17

Roof battens .............................................................................................................................. 19

Ventilation .................................................................................................................................. 19

Underlay ...................................................................................................................................... 20

Insulation .................................................................................................................................... 22

LITERATURE................................................................................................................................... 25

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INTRODUCTION

The roof is the most weather exposed part of the building.

The primary problem is moisture from the weather’s actions which, together with environmental pollution, break down the roof’s materials and

cause damage to the underlying structure and its building components.

The roof surface, which is built together with the underlying construction in the outer walls, gables, and floor construction, is discontinued

because of other characteristic construction elements like chimneys, dormers, fire-parapets and valleys – all of which present critical problems with regard to

water and weather tightness.

The traditional high-pitched roof presents, together with the façade of the structure, the architectonic face of a building.

In recent years new materials have came onto the construction

market. They claim to be cheap and rational in construction – but the manufacturers often forgot to give objective information about life-cycle-cost

and architectonic value.

To make a useful survey of a building it is necessary to have general

knowledge of construction technology so that the damage to the building can be recorded and the cause of problem be identified. It is important to gain

knowledge of local building traditions before doing an assessment of a building. Finally, it is important to have knowledge of how to repair damage and defects

in the building – whether they were caused by poor construction, bad materials, altered conditions, or the passage of time.

A number of considerations are important in connection with

renovation of buildings, among others: legal relations, the use of suitable building materials, investigation into fungus infestation, and the building’s

situation with regard to future maintenance and insurance.

This report contains 3 main sections:

Common information - knowledge of local building traditions Evaluation of the building – Where are the problems?

Directions – How to solve the problems and renovate?

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COMMON INFORAMTION

Building traditions The period from 1860-1950 is consisting of a series of architectural

trends ranging from Late Classicism to Industrialism.

European national architectural trends have influenced the form of roof and roof décor.

Regardless of these architectural trends, which around the turn of the century resulted in a large number of prestigious buildings with intricate

and complicated décor, the roofs primary constructions and materials remained the same.

Differences in local building traditions have limited themselves to

size and the number of floors in the building, rather than the differences in common practices of craft and workmanship.

There are examples of cheap design and construction techniques,

especially in buildings before the 1920’s where construction members like rafters and joists had been under dimensioned, resulting in sagging roof

battens due to too much space between rafters.

Roof forms

The outer form of the roof is a result of the underlying timber

constructions. Timber roof constructions, in the period we are considering, are

characterized by small number of construction types:

-Collar tie roofs -Collar tie with knee-brace

-Copenhagen roofs -Mansard roofs

-Trussed rafter roofs -The half-trussed roof.

In this report I will take a look

into collar tie roof only.

The even roof surface is broken

by structures like: dormers, chimneys, fire-parapets, staircase towers, etc…

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Collar tie roof

The Rafter Construction

In accordance with the Copenhagen Building Code of 1856, all rafter

constructions were constructed as saddle-roofs with maximum pitch of 45 degrees and the rafter itself fixed into the joists via a mortise. Later on in the

18 hundreds, a sole-plate (horizontal timber plank 50x100mm) was mounted on top of the joists and the rafters mounted on top of this. The roof was

symmetrical about the length axis of the building. In the code of 1939, rafter dimensions of 5x5’’ (130x130mm) and

6x7’’ (157x183mm) (1’’=26,154mm) were specified for both light and heavy

roof constructions with a rafter spacing of 1 meter. Originally, the collar tie rafters were mounted in pairs onto the tops

of the joists with mortise, approx. 6-8’’ (157-209mm) from the joist ends. The rafter and joist distances were, therefore, identical at about 1,5 Alen = 3 feet

(942mm). The ridge end of the rafter was joined with mortise and a slash,

secured with wooden dowel (cylindrical wooden bolt). The minimum rafter was fixed at 5x5’’ (130x130mm).

The collar tie was used to stiffen the rafters and the whole structure was stiffened in the longitudinal direction by stud wall on either side. The collar

tie was fixed to the rafter with a mortise and tenon joint with dowel. In the 1880-90’s a sole plate was mounted onto the joists and the

rafter-foot saddled on top of that. Thus, the joist and rafters became independent of each others.

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Roof Eaves

Roof-Joists

The roof-joists and therefore the roof is anchored in the same way as normal joist-layers, i.e., bricked in steel anchors. The anchor is nailed to the

side of every third joist and bricked into the back and facing brick of the massive or cavity wall.

The partitions in the roof storey are part of the supporting and shoring system of the roof.

The eaves construction

along the facades of a building became common around 1920. The

protruding rafter ends were either cut vertically or horizontally and the

underside of the rafter ends were clad with timber soffit-boards, or boards

were nailed to the top of the rafters, between the battens, and they were

visible from beneath. The verge at the gable protruded. The gable rafter was

supported to the battens, but

sometimes supported at the facades by a cantilevered wall-beam. The roof

cladding was completed with a 1,5x8’’ (39x185mm) timber Barge-board and

a cover board.

When the roof-joists

were constructed, consideration was taken to the fact that the rafters

had to rest on them. The roof-joist layer is different to that of the floor-

joist construction and dependent on the roof form.

Where main cross partition walls, or party walls, were

bricked to the roof storey, the joists were often supported by these

walls.

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Roof Claddings and Roof Flashing

The traditional roofing materials which were most widespread in the period up to 1910 were pan tiles, natural slate tiles and zinc-plate cladding.

Later a number of cheaper products like bituminous roofing felt, cement roofing tiles and asbestos-cement corrugated and slate cladding came onto the

market.

Insulation

Before the 1950’s insulation of roof construction was only done to a

very modest extent. It consisted mainly of laying 3-5 cm of mineral wool mats in the loft room.

Roofing

The most widespread roofing material is the Pan tile which is able to absorb any in-accuracy on the construction of the roof surface.

The roof tiles were bound to the battens with copper of steel wire through holes in a protrusion on the underside of the tile. Usually every 3rd to

4th tile is bound. After the roof was laid down, the underside was pointed with

mortar, which was’ occasionally reinforced with cattle hair. The ridge and hip-ridge are covered with a special ridge tile which is bound or nailed to the roof

construction after bedded in mortar.

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EVALUATION OF THE BUILDING

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DIRECTION - How to solve the problems and renovate?

Vapor barrier Vapor barrier is to prevent the hot humid air from penetrating

into the structure at which the cold periods will condense, at the risk of attack by rot and mold.

Most moisture problems associated with vapor barriers, either

because it has been misplaced, or that it is not close.

Especially cause the performance of joints, connections and penetration problems.

Injuries often occur during or immediately after the setup of the

vapor barrier. This happens for example when DPM is damaged when cables

and wires must be installed and assembled.

The vapor barrier must always be placed on the heated, interior side of the insulation. The safest location of placing the vapor barrier is

inside the insulation where it is better protected against perforation.

To avoid condensation in the insulation layer, it is important that the vapor barrier maximum placed 1/3 inside the insulation layer from the

hot side. In this way, electrical installations, etc..., can be installed without

major risk of the vapor barrier to be destroyed.

On wood the vapor barrier has to be setup with staples or

possibly clout nails. On steel frame erected vapor barrier has to be setup with double-

sided tape, if necessary it can be glued with glue by the supplier. Joints, connections and penetrations should always be established

on a stable surface for the vapor barrier so that it can be performed close.

The substrate must be firm and level, so the materials tightly together. The vapor barrier should be erected at a late stage, such as

immediately before completion of insulation and installation of ceiling tiles or shuttering. In this way, the risk of damage is limited to a minimum.

The vapor barrier must always be set before heating begins, else moisture can penetrate into the structures.

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As a rule, all connections are performed as bonded solutions to be achieved good air tightness. Bonded solutions used here as a generic term

for solutions that are done with tape or sealing tape. Collections must be carried out over a backstop, such as a board or plate piece, and they must

have an overlay of at least 100 mm. Connections made with strips or tape to be printed after installation, eg

nylon roller or a squeegee.

Connection of vapor barrier done with tape

Connection of vapor barrier done with sealing tape

A new vapor barrier will usually be cheaper and easier to install in connection with the renovation than afterwards, when you have found that

moisture up into the roof structure.

Seal performed with sealant between the vapor barrier and wall.

Interior trim omitted.

Vapor barrier and sealing tape squeezed against the wall with shadow list.

When connecting to other

materials must be used grouted or cemented joints. There must be a substrate for sealing

or gluing, for example, a board or a piece of sheet metal. Sealing or bonding must be

carried out with suitable sealant, sealing tape

or tape must be compatible with the applied vapor barrier.

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Penetrations must always be established anvil behind the vapor barrier, e.g. in the form of a plate. The abutment must be sufficiently rigid

for attaching it to pass through the vapor barrier, such as a ventilation duct. In this way the materials can be maintained in relation to each other, and it

is more opportunity for a good and durable assembly. Vapor barrier's connection to the bushing must be as close as

possible and be maintained with tape or sealing tape. There must be sealed between the vapor barrier and penetration with a suitable sealant.

Damaged vapor barrier before set up clothing, it must be

repaired. Repair of holes with diameters up to 50 mm and cuts up to 150 mm can be made with impermeable tape (follow manufacturer's

recommendations on the tape). For larger damage repair is carried out with a new piece of vapor barrier, which is mounted over the damaged surface

with an overlay of at least 100 mm in all directions. The new vapor barrier

Example of duct passes through ceiling. Steel collar mounted to the surface with jointed between the collar and vapor barrier and between the collar and the channel.

Vertical section of a roof construction

with a ventilation channel carried out as shown in the upper fig.

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must be maintained on a stable surface on at least two opposite sides, and the joint between the injured and new vapor barrier should be taped.

It is important that materials for vapor barrier tape and sealing

tape mm selected with great care. To select a vapor barrier, see BYG-ERFA Sheet No. (39) 07 10 29,

"Vapor barriers in the building envelope - Moisture Transport and materials”

Flashing

Experience shows that flashings with stepped loose edges by oblique

along tracks between roof and wall have fewer leaks and require less maintenance than flashings with just loose edge that is mounted in a parallel

to the roof surface.

Where sloping roofs meets vertical

restraints, such as masonry, there is usually covered with

metal flashings, which consists of deposits and

loose edges. Flashing is to

ensure that rain water and snow do not penetrate the roof and the lower parts.

1 – Roofing felt cover between

eaves and masonry. Height must be min. 100 mm above the roof tiles.

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Straightening

2 - When the roof battens and roof

tiles are installed, deposits of 0.6 mm soft level zinc plate are placed on

each tile. Deposits are secured with 2 pcs. of galvanized nails in joints. The

deposit is formed by the tile, and it is carried out with the overlay up under the overlying tile.

Cover by horizontally

along wall

In the case of roof refurbishment of older buildings should be

set up roof with great gentleness. If the roof construction such as hanging or

shooting back, you often have to respect deviation to ensure that the building

retains its authentic character, and to the roof surface can adapt to the building

other imbalances.

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Before straightening of rafters, must be made an overall assessment of the

roof structure, which includes the rafters checked. It may be necessary to perform the locking, so as to ensure that there is no excessive distance

between rafters of the eaves and roof battens.

Demolition

The original rafter structure is

preserved.

When existing roofs, beams and eaves etc…, are

demolished, the work has to be planned and executed carefully.

The environmental

and safety regulations must be observed, so roof structure

stability is maintained both during and after construction.

The best way to fix

the alignment planks is with through bolts. The advantage

is that existing rafters and

alignment plank can be tightened so hard together to

achieve a good transmission assembly, although alignment

planks shrink slightly after installation.

There must always be a calculation of the plank

dimensions and mounting distances etc… by a structural

engineer.

16

Damage from fungus, rot and insects

To avoid the natural decomposition of tree, it should be dry. The

wooden structures, which wood moisture for a long time is higher than 20%,

there is an increased risk of attack by fungi and insects.

Typical places to rot, fungus and insect attack are especially at

the eaves, gable and fire-parapets where trusses, braces and beams can be in direct contact with masonry, there is an increased risk of attack by fungi.

However, even in locations where wood is not in contact with the masonry, for example, by valleys, rear chimneys and skylights, it is found that often

afford, fungal and insect attack.

In light attacks, it is not always necessary to repair or replace the

tree. One by impregnation and reinforcement of the affected wood with fishplates of pressure-treated wood may be sufficient. At the same time the

source of moisture to be removed - for example, repair of the roofing.

In severe attacks, it is often necessary to cut rafters or beams ends and replace them with new wood.

If the roof is wrong done,

or it is not been properly

maintained, the roof construction

has been exposed to moisture. This

means a high risk of attack by fungi

and insects.

17

Roofing

Central to all roof is of course the roof covering, which plays a

vital role in building resilience to weather - and thus for the entire lifetime.

Therefore, in addition to the considerations relating to the

building's appearance - and the requirements that must be asked to roofing materials and slopes in local plans, etc… - Exercised great build technical

diligence when it comes to roofing.

For all types of roofing tiles, there must be air-gap at both the bottom of the roof, the ridge roof valleys and ridges, corresponding to a 200

cm2 free, through slot per. lbm. by Body Depth of up to 8 meter

New and old wood

assembled with lugs and

through bolts

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At least every other tile to be bonded or otherwise maintained.

They tied stones to be distributed diagonally on the roof.

In addition, all tiles should be bound in the following areas:

-In the lower (interlocking tiles) or second lowest (wing tiles) number at the

eaves. -The outermost row of gables.

-Along the valleys. -Around dormers, skylights and other penetrations into the roof.

-In the top row along the mortar-free ridges and burrs.

Every other tile bind (dark rock). The bound stone divided diagonally on the roof surface.

If the tile is cut to length, they must be secured with the screw. If

the tiles are fixed with screws, use stainless steel screws in the dimensions 6.0 x 60 mm with neoprene washers. Roofing tiles, which are screwed,

have to be drilled first.

Roofing tiles secured by a screw.

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Roof battens

It is a prerequisite for the roof that it will be closed, durable and achieves the expected appearance. Roof battens must be fastened properly,

as they help to stabilize the roof.

If roof battens are not properly installed, there is a risk that the whole roof can occur in the storm.

With effect from 1 January 2006, the roof battens for all types of

roofs, as well as with outside eaves, must meet the requirements of the new trade agreement for T1-roof battens. This means that the future T1 batten

dimension is min. 38 x 73 mm when the rafters are up to 1 meter. This change has been made to strengthen the safety of traffic on roofs during the

construction period and to better batten quality. T1-roof battens in the dimension 38 x 56 mm can continue to be used by rafters up to 75 cm.

T1 labeled batten

Ventilation

Moisture Damage in roof structures often occur, because warm

moist air from the room during cold periods escaping in the outer parts of the roof and condenses. Properly performed ventilation with outside air -

between insulation and roofing - has proven to be an effective way to prevent moisture damage in isolated frames, provided that the ceiling is a

dense vapor barrier.

Lack of ventilation of the roof structure will often result in injuries

that manifest themselves as attacks by fungi.

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When using impermeable underlay, the establishment of a ventilated cavity between the roof and insulation material is mandatory.

The vented cavity to be carried out with an average height of at

least 50 mm. Underlay of rail products will experience hang slightly between the rafters, they should be projected by at least 70 mm height of

the cavity.

Vent areas shall be in accordance with the SBI instruction No. 178.

Distribution of ventilated air for buildings with roofs up to 12 meters

Underlay One of the most important parts of a roof is the underlay. It plays

an important role in that no water can penetrate into the building - and thus

the life of the roof. Therefore there must be extreme build technical

diligence when it comes to the underlay.

21

Experience shows that the diffusion open underlay is less effective for wetting of the underlying structure. This is often caused by

condensation due to the fact that there is established a dense vapor barrier. Wetting can also be caused by leaks. The best underlay obtained by to lay a

solid underlay to the entire roof surface. When selecting roofing and choice is between different types of

underlay it should be took under consideration the following service classes:

- Low (L)

- Middellav (ML)

- Medium (MH)

- High (H)

High is the class used for the greatest demands of the underlay. What class

to be selected depends on the roof, as the underlay is included in. There are five factors that determine which requirements should be put to the roof:

- Type of roof coverings

- Roof angle

- The complexity

- Availability

- Climate Impact

A distinction is made between high and low complexity. A simple roof with a

simple penetrations have a low complexity, while a roof with large penetrations or relatively difficult details have a high complexity. If the roof

has one or more of the following details, is the case of a roof structure with high complexity:

- Valley

- Large duct

- Chimney

- Attic

If the roof is rated for high complexity, it is synonymous with solid underlay, for example. roofing felt on the boards, while constructions

rated for low complexity often makes it possible to use a roll underlay.

22

Insulation

1. Pitched roof with ventilated cavity between the insulation and rain protection.

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2. Stud wall

3. Collar beam ceiling

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LITERATURE

BPS Publication 103 – Renovating apartment buildings: roofs

Roof & Low Rise Housing – by Roger Taylor

SBI 189

Damp proof membranes and sealants – BYG-EFRA

Ventilating roof structures – BYG-EFRA

Traditional solid underlay with pan tiles – BYG-EFRA

www.godetage.dk

www.isover.dk

http://www.danskebygningsmodeller.dk