Technical Advice on Windows & Window Details

Listed Buildings

Conservation in Tendring

1

This advice is provided to guide those preparing applicationsfor planning permission and/or Listed Building Consent.More general advice on both Listed Buildings and buildingsin Conservation Areas can be found in the two advisoryLeaflets which are related to this series of publications.

2

IntroductionWindows are an important feature of any Listed Buildingand they comprise a very significent part of the building’shistory. They are the single element which most serves toestablish the character of the building. Traditional, historicwindows are such an important part of a Listed Building’sfabric that they should always be retained and repairedrather than replaced by modern examples. This leaflet highlights the case to retain historic windows inthe District’s Listed Buildings.

Repairs

With all work to windows it is important to assess what youare dealing with historically before you start. The followingguidance in this publication will provide a useful overview ofthis, whilst the publications referred to at the end of theleaflet give even more detailed guidance. Applicants andtheir agents are strongly recommended to refer to theseother documents.

Traditional windows themselves are composite structures oftimber, glass and metal, each part of which can be repairedas a separate element when required.

Whenever possible theoriginal fixtures and fittingsof historic windows (hinges,catches, pulleys, handles,stays etc.) should be keptfor refurbishment and re-use on the window being repaired.

1

2

Traditional, historicwindows in ListedBuildings should beretained and repairedrather than bereplaced

Repair to wooden window frame

Various historic window styles, Harwich

Old illustrations of glass making

3

Glass

When carrying out repairs to historic windows it is importantto save for re-use any old glass, which can be carefullyremoved from old frames by a skilled joiner. This hasirreplaceable qualities of unevenness due to the originalprocess of manufacture : cylinder glass was produced byopening out a large blown cylinder of glass whilst Crownglass was produced by spinning a large disc. The centreof this disc, where the pontil was attached, is the bullseyewhich was generally used in an out of sight location orrecycled rather than used as a fake picturesque add on as itis today. The flaws in historic glass catch the light and showoff defects which cannot be found in modern glass.

Horticultural glass is a modern substitute that exhibits suchdefects to some degree and can be used in repairs. Whenreglazing sash windows, care should be taken to adjust thesash weights for any change in the balance of weightscaused by different thickness of glass. In general uppersashes should be slightly lighter than the weights, whilstlower sashes should be slightly heavier. Any glazing shouldbe undertaken using a traditional linseed oil putty ratherthan modern compounds. Timber beading, which increasesthe apparent thickness of glazing bars, is particularlyunwelcome.

Frames

Careful repairs to timber work, maintaining the maximumamount of historic fabric, are preferable to carrying out newwork. New sections of framing can be pieced in to matchthe glazing bars replaced, using existing parts as a pattern. Itshould be noted that casement frames were traditionallyinset within their overall frames, rather than projecting proudof their surrounds as in the weathered casements so popularamongst modern mass-produced window manufacturers.

Sashes can be easily removed from their frames byremoving the staff beads on the inside. Sashcords caneasily be replaced, access being gained to the sash weightsvia the removable pockets at the bottom of the pulley stiles.Replacement cords can be in jute, cotton or nylon. Thestyles of sashes should not be painted but lubricated with

3

4

Horizontal sliding sash window

Horizontal sliding sash window – local example

4

wax, and not eased after a building has remained empty forsome time as heat and ventilation can often do the trick.

The appropriate finish for historic windows after the 17thCentury is generally paint, most often white, and certainlynot a modern stain. For complete authenticity on a Grade Ior II* Listed Building, permission can be obtained to use atraditional lead based paint.

Window Surrounds

When renovating a window by repair it is important toremedy at the same time any defects in the surroundingfabric that may have initiated the original decay in thewindow. In this way the repaired material can be guaranteeda longer life. It is thus important to detail the surrounds toreplacement or repaired windows properly.

On rendered walls a lay board is often fixed above thewindow head to throw off the rain and give a pleasingshadow line. Moulded surrounds should be carefullyrepaired or reinstated using the original as a pattern.

Sill details are also important to maintain their projectionvarying with different window types. Timber sills areparticularly vulnerable to rot and if replaced should be ofoak or other durable native hardwood.

A History of Window Types

a). Windows originated in timber-framed houses asopenings within the frame provided to let light in : thediamond or square cross section mullions of early windowsgenerally followed the lines of the building’s timber framing.They were originally unglazed and usually had an internaltimber sliding or hinged shutter, the grooves for this beingthe only remaining clue to their former existence.

b). In the 16th Century. Along with the ceiling of rooms andthe provision of floors and chimneys to former open hallswindows began to be glazed. Small diamond shaped panesof glass, known as quarries were set in lead cames in fixedor opening iron casement frames within the overallmullioned framework. These usually had ovolo mouldingsproviding a ledge for fixing the lights using nails.

5

6

1 Top sash2 Staff bead3 Parting bead4 Shutter5 Fastener6 Bottom meeting rail7 Top meeting rail8 Shutter box9 Bottom rail10 Pulley11 Pulley stile12 Sash cord13 Outer lining14 Inner lining15 Sash stile16 Pocket17 Sash weight

Sash windowconstruction

1

2

34

5

6 78

9

10

11

12

13

14

15

16

17

Church Street, Harwich

c). In the 17th Century the mullion and transom type ofwindow was developed. Usually in oak with leaded lightglazing it represents a transitional type towards morevertically oriented windows. The basic pattern was still inuse in the nineteenth century but in painted softwood withnine large panes of glass.

d). In the 18th Century, with the greater availability ofsoftwood and larger panes of glass, the side hung timbercasement developed from mullioned windows as a cheaperform of construction. Usually with two lights it was lesssuitable for classical buildings but was commonly used indomestic and gothic style buildings where a central mullionwas acceptable.

e). Another more domestic type of window form is the“Yorkshire sash”, a horizontally sliding version of the norm,which did not require the elaborate counterweight system ofvertical sashes. This, as its name suggests, was moreprevalent in the North of England but there some examplesin Tendring (See page 3).

5

A Late 17th Century cross window with leaded lights

B Late 17th century eight over eight sash

C Early 18th century sash

D Early 18th century sash with segmental headed arch

E Late 18th century six over six sash

F Regency window with margin lights

Right: 15th Century former farmhouse,The Moot Hall, Clacton with squareleaded mullion and transom windows

Below: Ancient House, Ardleigh

A

C

E F

D

B

6

f). From the late 17th Century the double hung verticalsliding sash was increasingly used, usually in paintedsoftwood. This presented a more vertically orientatedopening in keeping with the fashionable classicalproportions being adopted for buildings. Early exampleshave quite thick ovolo moulded glazing bars and exposedsash boxes containing the counterweights, set flush with theouter face of the wall. Sometimes only one of the sasheswas hung.

g). The London Building Acts of 1709 and 1774 requiredfirstly that sashes be set back 4 inches from the wall faceand secondly rebated behind the wall face as a fireprecaution. These styles of sash boxes both spread asfashions to the provinces some 20 years later. Graduallythrough the 18th Century panes of glass became biggerand glazing bars thinner, using lamb’s tongue or ogeemouldings. By the end of the 18th century sash windowswere also produced with rounded or gothic heads, whilst bythe 1830’s the margin lights became fashionable.

h). In the 19th Century sash windows generally had fewerbut larger panes, as a consequence of improved methodsof manufacture, together with even thinner glazing bars.This left the sash frame vulnerable to stress and rotparticularly at the corners, and resulted in the introduction ofhorned sashes (see right) with a stronger through tenon jointfrom mid-century onwards.

i). Late Victorian / Edwardian (Early 20th Century)In the late Victorian and Edwardian period the Arts andCrafts style properties produced sash windows withsegmental heads, flush sash boxes, and sometimes ArtNoveau style leaded glazing in the upper sashes. Theyillustrate the influence of the Queen Anne revival at thattime. Also during this period there is considerable evidenceof a revival of the flat frame casement window.

The Library, Frinton-on-Sea displayingvarying window styles

Early mullion window originally unglazed

Ringed - Horned Sashes

The Grand - Clacton (1897)

The insertion of factory made standardwindows of all kinds is almost alwaysdamaging to the character and appearance ofhistoric buildings

j). Metal framed windows - 1930’sDuring the 1930’s Modern Movement or Art Deco buildingswere constructed with mild steel windows. The largestsurviving group of such buildings in Tendring District can befound in Frinton where at present three examples are listed.The retention of the original steel framed windows is animportant factor in the conservation of these buildings butwhere replacement is considered necessary exact copies ofthe originals must be sought.

Glazing Bars

The earliest glazing bars of both sash and casementwindows were numerous and thick. On the inside they weremoulded to deflect light and reduce glare. On the outsidethey were rebated to take the glass pane, held in place byputty as they are to this day.

Over the years the cross-sectional area of glazing barsgradually reduced, eventually reaching a point in the late18th and early 19th Century when width was as little as13mm (half an inch). As a result these narrow bars wereoften made of hardwood or even metal. At the same timethe size of the glass panes increased considerably.

7

7

Church Street, Harwich

Impressive Listed Building group inHarwich with various window styles

Modern Movement ( 1930’s)buildings in Frinton

New Windows

The complete replacement of windows should only be a lastresort and in a Listed Building this will require consent. Ifthis is done, particular attention should be paid to the use oforiginal mouldings and accurate setting out to the originalpattern. With replacement casements the inclusion ofaddtional night vents unbalances a window’s elevation andis inappropriate. Most historic windows have alreadysurvived periods measured in hundreds of years, althoughonly constructed of deal, a slow grown pine. If properlyrepaired and reasonably maintained they can be expectedto last at least as long again.

Additional or redesigned windows in a listed building, orextension to it should always follow the design criteriaalready mentioned and be based on authentic precedents.

Applications for Listed Building Consent and PlanningPermission for replacement windows must be supported bysufficiently detailed scaled plans at least 1:20 scale. Suchplans must depict not only the overall window opening butalso the constituent parts of the frame, including the openinglights. The proportions and widths of the glazing bars mustbe shown which is best done by a combination of detailedelevation and large scale section through the frame.

8

8

SourceHampton Court Cupola of Eagle

House, MitchemDate1689-94 1705Width40mm 30mmDepth42mm 33mm

Glazing Bars

SourceBerners The Barons Beford SquareLondon Reigate LondonDatec1750 1721 1775-86Width22mm 19mm 15mmDepth44mm 32mm 40mm

SourceTypical Victorian Typical modern‘lamb’s tongue (repo) double glazing barWidth15mm 45mmDepth35mm 64mm

Late 19th Century windows, ChurchStreet, Harwich

Six over six Sash Window, Harwich

Impressive three storey bay windowsin Grade II* Listed Building, Harwich

9

9

Plastic or sprung V or Z -strip

Glued or painted siloconerubber tubing

Parting bead (Ventrolla)

Meeting rail brush (Ventrolla)

Bottom sash or sill brush(Ventrolla)

Parting bead weatherstrip(Mighton)

Brush for meeting rails(Draughtseal)

Standard weatherstrip(Mighton)

Staff bead or button rod(Ventrolla)

Silicone seal (Draughtseal)

Diagram of differentwindow insulation

1

2

3

4

5

6

7

8

9

10

1

2

3

4

5

6

7

8

9

10

1 23

47

5 10

89

6

8

Retaining and Improving Existing Windows

Where original examples exist they should be repaired whereverpossible rather than be replaced. If replacement is unavoidablethen the new windows should be historically accurate.

Modern, usually double glazed replacements in metal orplastic frames are definitely not appropriate in historicbuildings. The relative improvement of comfort with double-glazing is very little in an older building where the walls canaccount for the major proportion of heat loss.

Whilst still maintaining the existing windows, the improvedperformance of modern windows can be achieved in anumber of different ways which have less impact on thehistoric fabric. These include the use of draught strips,secondary glazing and the refurbishment of original shutters.Further information is shown in the English Heritagepublication “Energy conservation in traditional buildings.” 2008.

Redrawn from English Heritage publication “Energy Conservation in traditional buildings

Listed Buildings - Applications for Consent

Applications for Listed Building Consent do not attract a feewhich is a recognition that there is a cost incurred inpreparing the necessary quality of plans required toaccompany such applications. The Council strongly advisesthe owners of Listed Buildings to engage properly qualifiedand experienced professionals to prepare such applications.

Such professionals can also provide advice on methods ofrepair. Wherever possible the Council expects owners ofListed Buildings to explore repair of historic fabric ratherthan seek to replace it with modern materials.

The advice in this series of leaflets draws on a variety ofspecialist publications prepared by other organisationsincluding Essex County Council, English Heritage, S.P.A.B.Links to these publications and/or the organisations’ websitesare given at the end of each leaflet.

Further information

The Georgian Group Guides No. 1 Windows

SPAB Technical Pamphlet 13: The Repair of Wood Windows

English Heritage Listed Building Guidance Leaflet: Sash Windows

English Heritage Listed Building Guidance Leaflet: Dormer Windows

English Heritage Window Comparisons Framing OpinionsLeaflet 5

English Heritage Energy Conservation in Traditional Building 2008

Essex County Council: The Conservation and Renewal of Timber Windows 2000

Windows: History, Repair and Conservation. Donhead 2007.

Other usefulsources ofinformation?There are various nationalorganisations providing designadvice and guidance in relationto Window and WindowDetails. These include thefollowing:

English Heritagewww.english-heritage.org.uk

Historic Environment LocalManagement - HELMwww.helm.org.uk

Society for the Protection ofAncient Buildings - SPABwww.spab.org.uk

The Victorian Societywww.victorian-society.org.uk

The Georgian Groupwww.georgiangroup.org.uk

The Twentieth Century Societywww.c20society.demon.co.uk

Institute of Historic Building Conservationwww.ihbc.org.uk

Historic Towns Forumwww.historictownsforum.org.uk

Essex County Councilwww.essex.gov.uk

Communities and Local Governmentwww.communities.gov.uk

Note; Tendring District Council is not responsible for the content ofany external websites.

10

10

11

Windows & Window DetailsFor more information write to:

Planning ServicesTendring District CouncilCouncil OfficesWeeleyClacton-On-SeaEssex CO16 9AJ