Maintaining Timber Windows
A well-maintained timber window is a crucial element of the historic fabric of a structure. It illustrates in varying degrees the different materials and technologies design, craftsmanship and aesthetics of the time period that it was built in.
When possible, repairs should be made on-site. Proprietary resin-based repair systems can be used to repair the most damaged areas of decay without having to remove the entire window.
Durability
Timber windows were built to last hundreds of years. They require regular maintenance to keep them looking good. The most common maintenance tasks include repairs to sash cords as well as tightening sash pulleys and painting. There is a growing need to upgrade timber windows to improve energy efficiency. This could include replacing old glazing units, repairing the window rebates that are in place or installing new cills for improved air seal.
One of the major issues with traditional windows is damage caused by corrosion of the paintwork. This is particularly true when windows with sash are involved since the gaps between sashes can be very large. In these cases, water can penetrate paint film and cause rotting of the wood or putty beneath. The weather can be a factor in accelerating the rotting. To prevent this windows, they should be painted regularly with a suitable exterior wood paint.
Corroded areas should be repaired using resin-based products. This will ensure the maximum amount of the original fabric is retained. It is also essential to minimise the number of holes you drill into the frame for cable entry since these could allow water in and cause decay.
Another issue with older windows is the structural movement within the wall which could cause deformation of the frame and the sash. This could result in the sash not fitting properly, sticking or jamming in the opening and cracked glazing. Most often, this is corrected through the installation of new sash boxes made from slow grown deal (pine) or oak. The cill needs to be constructed of a strong hardwood like oak, in order to prevent any differential movement between new and existing work.
To reduce the risk, there are now several companies that make Boston pattern sash made of wood that will fit most existing openings. They are available in various sizes and finishes that fit the needs of modern-day homeowners. In conjunction with quadruple draught strip and better thermal insulation these new sash can make an enormous difference to the energy efficiency of a house.
Aesthetics
A lot of old timber frames have a great aesthetic appeal, since they reflect, in some form, the quality of the wood, technology, and architectural aesthetics of the time they were made. They may also have significant historical value in their individual cases. This is especially true of windows that were unglazed in the early days of timber-framed buildings, where the great majority were simply a series of openings within the frame, which were divided horizontally into mullions, and vertically into wood or iron bars to keep out invaders.
It is essential to preserve the appearance of traditional timber window joinery. As soon as you see any signs of decay due to water penetration it is essential to stop it. It is recommended to do this through thorough painting, especially if there has been damage or deterioration. It is recommended to use paints designed to be used in a system (primer undercoat and finish), and to follow the manufacturer's guidelines for preparation and number of coats at each stage.
Wet rot is a common problem for older timber windows. The best way to stop it developing is to remove any damaged or rotten sections as soon as possible to stop the spread of the fungus responsible for it. Replace the wood that is rotting with slow-growing deal (pine), and when possible, the exact type of wood as the one that is being removed, to avoid any differential movement.
Glass became cheaper and more abundant during the late medieval period and into the 17th century. This led to the openings for glazed windows on timber-framed houses became more complex with moulded mullions, tracery made of wood and deep cills projecting into the air. The glazing was increasingly laid within rebated frames and secured with 'glazing sprigs', rather than into lead cames. This method of glazing is not only less prone to leaking but also allows for larger and clearer sheets of glass to be used in the windows than would otherwise be possible without the need for lead lights.
Energy efficiency
Traditional timber windows are energy efficient because of their thickness and multilayer construction as well as care for the smallest of details. They also have large glass areas and deep projecting cills that minimise air infiltration. The windows can be made to improve their energy efficiency by draught-proofing and secondary glazing. However, it is important to remember that such measures should be evaluated in terms of the overall integrity and appearance of the original window.
So, retaining existing historic windows that are in need of repair instead of replacing them makes sense, particularly when their thermal improvements can be achieved economically through simple repairs and upgrades. The windows that are historic have a lot of historical significance, since they reflect a variety of technological advancement and changes in architectural style. The pressure to replace these windows are usually based on the assumption that old windows will need replacement in the near future, but the majority of them are in a position to last for 150, 200 and even 250 years if properly maintained.
It is crucial to recognize that the decay issues caused by traditional timber windows can be avoided through regular maintenance and swift repairs. It is also crucial to recognize damp issues and address them promptly so that you can avoid serious damage. Paint deterioration that occurs early is a concern because it allows moisture to get into the wood, which can cause wet rot. This damage is often not noticed until the paintwork becomes cracking or wavy, but can cause significant structural damage and can lead to further decay.
A quality paint will prevent moisture penetration. It is also important to keep the paintwork in good condition in order to prevent condensation and mould growth. The use of modern synthetic paints could be a problem because they are usually formulated to be water-resistant, and this can lead to the formation of mildew in the window frame.
Most older windows were made of sapwood-rich timber. These timbers are susceptible to deterioration rapidly if exposed to wet weather, but can be protected by a thorough preservative treatment before they are used. It is also essential to ensure that the type of timber used is well-suited to the location and climate conditions, as these elements will influence the durability of the joinery. Local window manufacturers offer various types of sash timbers that can be customized to fit historic openings. They can be built to the standard Boston pattern dimensions, or to custom sizes that are in keeping with the historic architecture.
Maintenance
The lifespan of windows made of timber can be extended by regular inspection as well as a careful redecoration and prompt repair. The primary cause of wood decay is moisture leaking through deteriorated paint and putty. This can be prevented by careful painting and window fitters cambridge the use of a good quality wood preservative.
Repairs to old sash windows and window frames made of casement should be done with care and with minimal disruption. It is possible to fix the majority of traditional wooden window designs without removing the frame. This is a must whenever it is possible. Remove any peeling or loose paint and lightly sand the area to improve the "key" of the surface. This will allow the new coating to stick better. Care should be taken to avoid stripping old paint layers which may have historic value, and where these are present, it is recommended that a paint analysis be conducted.
When a piece of wood has become rotten the best option is to remove the rotted material and replace it with spliced-in timber inserts that are shaped to match existing profiles. The inserted wood should also be treated with wood preservative and the connection between the timber cill and the masonry sub-cill should be sealed.
Replacement of traditional windows with PVC-u may be an appealing option, particularly when the installer offers a "one-stop shop" installation that takes care of removal and replacement in one day. It is crucial that installers of replacement windows have a thorough understanding of the history and construction of traditional timber frames. This will enable them to make appropriate recommendations for energy efficiency improvements and other technical improvements that will not harm the historical character of a building. Anyone who installs replacement windows must be registered under a Competent Persons Scheme such as FENSA. This will ensure that the replacements are deemed as a suitable solution under Building Regulations. It is certainly possible for an experienced and skilled carpenter to install PVC-U windows that match the style of the building originally. This is especially true when the windows are situated within listed buildings or conservation areas.