The Repair and Replacement of Traditional and Historic Windows

Transcription

1 information sheet The Repair and Replacement of Traditional and Historic Windows Introduction This information sheet is intended to act as a guide to those considering the repair or replacement of windows in historic buildings, whether listed or within designated Conservation Areas. The principal types of windows referred to are sash and casement windows; these are the most common historic styles evident within the County Borough. Other types and style of window do exist and whilst the general principles outlined within this document will apply, further specialist advice may be necessary in some instances. Why are windows so important? Windows form one of the most significant constructional elements of a building and their style and proportion vitally affect the character and appearance of a building and its surroundings. Windows also provide important evidence of the origins and historic development of a property. appearance are often more desirable and sought after and unsympathetic alterations may impact upon the financial value of the property. The alteration of windows may seem to have insignificant effect but even simple changes can impact upon the whole appearance of a building and detract from the traditional and historical character of the building and the surrounding area. The detailing of any repairs and of replacement windows is therefore crucial to the sympathetic conservation of Wrexham's rich architectural heritage. Buildings which retain their traditional This leaflet is available in accessible formats Wrexham County Borough Council

2 General Principles Repair before replacement. Repair, particularly of original windows, should always be the first consideration. Most can be repaired and this is the best way of conserving the character and fabric of a historic building. Like for like replacement. Where original and traditional windows are beyond the repair of a skilled joiner then replacement on a like for like basis, that is an exact copy of the existing window, should be the next option. Avoid introducing modern-style windows. Most modern window types, such as the 'standard' 1.8 metre wide frames and tip-opening lights are only appropriate in modern buildings and almost always look out of place and incongruous in historic buildings destroying the original design intentions. Avoid double glazing. The introduction of double glazing can completely alter the proportions of the window frame and size of the glazing bars and frame necessary to carry the units. They can therefore significantly alter the overall appearance of the building. Slimmer profile double glazing systems are being developed which may be acceptable in some instances, however this technology is very early on in its development. Original single glazed windows should never be replaced with double glazed alternatives. Avoid PVCu windows. PVCu is not a traditional building material and is unsuitable for use in historic buildings negatively affecting the appearance and the ventilation of the building. Arguments that PVCu is more sustainable and environmentally friendly will not be accepted as sufficient justification for its use in historic buildings. Consider other methods of insulation. Some window openings can accommodate secondary glazing which can be removed in the warmer summer months. Draught proofing and weather stripping existing windows can also aid thermal insulation as can heavy, lined curtains. Retain original window furniture. Window furniture forms part of the intended window design. Where replacement is necessary and original window furniture exists this should be retained, repaired and reused as far as possible. Any necessary new window furniture should match the designs, size and material of the original. glazing bars Use appropriate methods of repair. Methods of repair should be appropriate to the window material and the age of the window. Using original techniques helps ensure compatibility in terms of performance and design. Traditional techniques such as splice repair and use of linseed oil putty are encouraged. The use of modern compounds and wood fillers will not be accepted. head sash box Components of a sash window pulley wheels sill sash cord counter weight bottom rail

3 Maintain the original position of the window frame within the reveal. The position of a window within the reveal not only contributes to the character and appearance of an elevation but also provides evidence as to the age and development of the building. Regular maintenance. Windows require regular maintenance and checks to ensure their longevity. Regular checking can draw attention to any potential problems such as rot or failure of elements of the frame, and can prevent the need for expensive and complete replacement. Redecoration maintains the traditional character and appearance and can help retain the maximum value of the property. Repair Sympathetic and careful repair is always preferable to replacement. The decay of traditional timber windows is most often caused by moisture penetration which can be easily prevented by regular checks and maintenance. Where rot has been detected within a frame it is important to identify and eliminate the source of the moisture and promote the drying out of the timber. Where possible the window should be repaired by removing the affected sections and splicing in new timber sections. This approach retains the historic fabric of the building and conserves the character by retaining the visual appearance. It is essential with the repair of sash windows that any repair ensures that the weight of the sash frame remains the same to allow the counter-balance mechanism to function correctly. Both sash and casement windows should be repaired using traditional putty. Glazing beads and modern compounds are not appropriate. Replacement Replacement will only be considered if the original or traditional windows are beyond repair. Like-for-like replacements must exactly match the design, detailing, proportions, materials, finishes and method of opening of the existing window so that the special character of the building and the area is conserved. Justification for complete replacement will be required. If modern or unsympathetic windows are to be replaced with a more sympathetic style then it is important that the detailing, proportions and design are appropriate to that building. Neighbouring buildings or historic photographs may provide clues as to the original style. Alternatively Conservation Section can assist in determining the appropriate window design. Historic Glass Some historic windows may retain their original stained, crown or cylinder glass. This glass is of significant interest for its age, rarity and also the finish which is detectable by the irregular surface which results in a distorted view. If a window is found to contain historic glass it should always be retained and reused

4 wherever possible. Great care is needed to remove the glass and it should always be stored safely during renovation works. Replacement glass can be sourced from specialist companies or salvage yards. Horticultural glass may also be considered suitable in some instances as it displays similar characteristics to historic glass. Iron Casements and leaded lights Historic leaded and metal frame casements are an increasing rarity. Wrexham contains many historic buildings which have metal framed windows and/or leaded lights as part of their original design which should not be lost. Whilst metal windows often appear beyond repair, in most cases they can be retained and repaired successively and this should always be the first option. Common problems with metal windows include rust, distortion, failing of hinges and fittings and build up of paint. Metal windows often have a very fine profile and frame and their aesthetic values, character and historic interest cannot be replicated in alterative materials. Where repair is not an option then like for like replacement should be undertaken. Extensive repair works and replacement of metal or leaded lights should only be carried out by a specialist. Which Windows should be avoided? The insertion of modern, factory made standard windows of all kinds, whether in plastic, galvanised steel, timber or aluminium is almost always damaging to the character and appearance of historic buildings and will not be accepted as an appropriate replacement to traditional windows in listed buildings or buildings within Conservation Areas. PVCu - There has been a progressive and damaging trend to introduce PVCu windows in historic properties. PVCu is not a traditional building material and is unsuitable for historic buildings affecting the appearance and the ventilation of the building. PVCu windows have a crude appearance lacking the finer detailing of traditional windows. The size of the frame is usually much larger than traditional openings making the PVCu window an obtrusive, obvious feature. The chunky appearance and shiny finish is completely out of character with historic buildings. PVCu windows are never acceptable on a listed building and rarely on buildings within Conservation Areas. Steel/Aluminium - Similar to PVCu windows, steel and aluminium have a modern appearance that is out of keeping with the traditional character and appearance of most historic buildings; some listed buildings have original steel windows where replacement in modern steel may be acceptable. Modern materials are often better suited to modern buildings. Mass-produced modern timber windows - Factory produced timber windows are often made of poor quality softwood which has a short lifeexpectancy. Native hardwood is better and more sustainable. Modern timber windows usually have standard detailing that has little regard to the subtle detailing of the original windows. Commonly they include modern finishes such as storm proofing and trickle vents which are not in keeping with the character of historic buildings and they will not be accepted on replacement windows.

5 Double Glazing - There is an increase in demand for double glazing in historic buildings to help improve the thermal qualities of the building. Double glazing is usually impossible to install in existing frames without significantly altering the proportions and profile of the frame and glazing bars which generally need to be larger to accommodate the heavier and thicker glass. For this reason standard double glazing is not accepted in listed buildings and strongly resisted in buildings within Conservation Areas. Specialist companies do exist that can supply slimmer profile double glazed units which can retain the original and traditional proportions of the window. The use of such technologies may be considered appropriate where they replace non-traditional and/or unsympathetic windows and would enhance the appearance of the building. Detailing however must respect the traditional proportions, profile and finish appropriate to the building. This technology is very early on in its development and the effectiveness and life span of the double glazed system is still unknown. Plant-on Glazing Bars - The use of plant-on glazing bars is not acceptable. Traditional glazing bars form an integral part of the frame forming the supporting structure. Plant-on glazing bars are a modern and inappropriate interpretation for historic buildings and detract from their traditional appearance and character and can fail after a relatively short period of time. Modern stained finishes - The use of modern stained finishes on existing or replacement timber windows is not a traditional or sympathetic finish and will not be accepted. Historically, most external joinery would have had a painted finish and this should be repeated on any replacement windows. Most paint manufacturers have a 'heritage range' of colours and further information on appropriate colours can be found at the contacts listed at the end of this document.

6 PVCu and double glazed window units are commonly inserted in place of historic and traditional windows as a means of improving the thermal performance of a building. Whilst they require less maintenance they only have a limited lifespan and cannot be easily repaired with the whole unit often requiring replacement when elements of the unit fail. PVCu is not biodegradable or easily recyclable and takes many hundreds of years to break down in landfill and is therefore not considered as environmentally friendly as traditional timber. Historic windows, sustainability and thermal Performance Improving thermal insulation is a major priority for most home owners in terms of comfort, economy and reducing our 'carbon footprint'. This is a common argument used to support the replacement and alteration of traditional and historic windows which are often referred to as unsustainable. The retention of historic windows is, in itself, a sustainable approach. Historic windows contain embodied energy, this is the energy used when the windows were originally made. Retaining them therefore preserves this embodied energy and negates the need to expend more energy on replacement windows, which will need to be cut, shaped and transported. When properly maintained, historic windows can last hundreds of years and many historic properties within the county Borough retain their original windows. Within historic properties it has been estimated that 20% of heat is lost through the windows, much of it through the gaps around the window frames. The rest is lost through suspended and ventilated floors, open chimneys and roofs. Therefore replacing historic and traditional single-glazed windows with double glazed units cannot alone address heat loss. The thermal efficiency and performance of windows can be improved using more appropriate, discreet and often cheaper methods than replacement. These methods include: Use of heavy, lined curtains, blinds or historic shutters - This is perhaps the simplest method to improve efficiency. Where historic shutters exist they are an honest and effective way of reducing heat loss, draughts and noise. Draught proofing or weather stripping - these can often be fitted into existing windows discreetly allowing the character and appearance of the window to be retained whilst reducing heat loss and draughts. Secondary glazing - Some historic windows can be fitted with secondary glazing although this will depend on the size of the window recess and the window itself. When fitting secondary glazing units care is needed to ensure that historic joinery, brick or stone work is not damaged, that the appearance of the window is not altered and that it will not impede a means of escape from the building. Listed building consent may be needed to install secondary glazing into listed buildings and it is advisable to contact the Conservation section to discuss any proposals in more detail.

7 When is permission required? Listed Buildings -If you live in a listed building, that is a building recognised as having special architectural or historic interest, formal Listed Building Consent is required for any works which would affect the character, appearance and/or the special interest of the building. The following works to windows will require formal consent: Replacement windows, where the new windows are of a different style (Replacing inappropriate or modern windows in listed buildings with a more traditional and appropriate style still requires formal consent) Like for like replacement* Replacement of the window in a different material Changes to glazing from single to double glazing and vice versa or reglazing which would result in the loss of historic glass Repainting in a different colour *Like-for-like repairs and/or the replacement of windows in listed buildings may require Listed Building Consent dependent on the extent of the works involved. Early consultation with the Conservation Section is strongly advised to avoid any unauthorised works being carried out to the building. Conservation Areas - Planning permission is not normally required to replace or make alterations to windows on dwelling houses within Conservation Areas. However some Conservation Areas within the County Borough have stricter planning controls due to Article 4(2) Directions which require a planning application to be submitted for alterations to windows that include changes to the detailing, style, materials, method of opening and finish insofar that the window(s) are visible from a highway, footway, waterway or open space. Article 4(2) Directions are in place in the following Conservation Areas: Replacement Windows and Building Regulations Replacement window installations will not normally require building regulation approval providing the installation company are FENSA registered. For further advice please contact the Council's Building Control Team on Bangor on Dee Cefn Mawr Chirk Fairy Road Gerald Street (Within Grosvenor Road Conservation Area) Holt Overton Pontcysyllte Aqueduct and Canal Salisbury Park Ruabon Grenville Terrace (Within Ruabon Conservation Area) If you live in a Conservation Area without an Article (4)2 Direction and do not require planning permission to replace or alter you windows, you are strongly encouraged to follow the advice given in this information sheet.

8 information sheet Contacts Planning Services Community Wellbeing & Development Department Wrexham County Borough Council, Wrexham, LL11 1AR Tel: Cadw Welsh Assembly Government Plas Carew, Unit 5/7 Cefn Coed Parc Nantgarw, Cardiff, CF15 7QQ Tel: Society for the Protection of Ancient Buildings 37 Spital Square, London E1 6DY Tel: The Georgian Group 6 Fitzroy Square, London W1T 5DZ Tel: info@georgiangroup.org.uk The Victorian Society 1 Priory Gardens London, W4 1TT Institute of Historic Building Conservation 3 Stafford Road Tunbridge Wells, Kent TN2 4QZ The Twentieth Century Society 70 Cowcross Street London, EC1M 6EJ Tel: May 2011 g/graphic/xpress/conservation/informationsheets/maintenanceguide