Maintaining Timber Windows
A well-maintained and maintained timber window is a significant part of the historic structure of a building. It reflects in different degrees, the technology and materials of the time in which it was made, the design and craftsmanship.
If possible, repairs should be done in-situ. Repair systems made of resin can be used to fix the most deteriorated areas without having to remove the entire window.
Durability
The windows made of timber in many old buildings were made to last for centuries. They do require some maintenance to keep them looking great. The most frequent maintenance tasks are repairs to sash-cords, re-tightening sash pulleys, and painting. There is a growing need for upgrading timber windows to improve energy efficiency. This could include replacing old glazing units, repairing existing window rebates, or installing new cills to improve air seal.
One of the main issues with traditional windows is damage caused by the corrosion of the paintwork. This is especially important where windows with sash are involved since the gaps between sashes can be extremely wide. In these situations water can get into paint film and cause rotting of the wood or putty beneath. The rotting can be exacerbated due to weather conditions that are poor. To prevent this windows, they should be regularly painted with a suitable exterior wood paint.
The areas that are damaged should be repaired with resin-based products. This will ensure that the best possible amount of the original fabric is preserved. It is also essential to reduce the number of holes that are drilled into the frame for cable entry, as they could allow water in and cause decay.
Another significant problem with older windows is the structural movement within the wall which can lead to deformation of the frame and the sash. This could result in sash not fitting correctly, jamming or sticking in the opening, and broken glass. This can often be fixed by fitting new sash boxes made from slow grown deal (pine) or oak. The cill should be constructed of a durable hardwood, like oak, to prevent differential movement between new and older work.
There are now several companies that make Boston pattern wooden sash to fit most existing openings. The sash is available in various sizes and finishes to fit the needs of modern homeowners. These new sash, when combined with quadruple draft strip and a more efficient thermal insulation, could make a huge difference to the efficiency of a home's energy use.
Aesthetics
Many old wooden windows have an excellent aesthetic value since they usually illustrate, in some way the materials and technologies and architectural taste of the period from when they were built. They may also have significant historical significance as a set. This is especially true for early unglazed window openings in timber-framed buildings, which were simply a series of openings within the frame, which were divided horizontally into mullions and vertical wood or iron bars to keep out intrusions.
Traditional timber window joinery can be a stunning aspect of a building, and is crucial to keep it looking good. When you spot any signs of decay caused by moisture penetration it is essential to stop it. It is recommended to do this with thorough painting, particularly if there has been damage or deterioration. It is best to use paints that are designed to be used in a system (primer undercoat and finish) and to follow the manufacturer’s recommendations for preparation and number coats at each stage.
Wet rot is a common problem in old timber windows. The best way to stop it growing is to eliminate any damaged or rotten parts immediately to prevent the spread of the fungus responsible for it. The replacement of wood that is rotting should be carefully undertaken by using a slow-growing deal (pine) and, wherever possible, the same species as that which is being removed to prevent any movement differences between the new section and existing timbers.
Glass became cheaper and more abundant in the late medieval period and into the 17th century. This led to the glazed openings in timber-framed homes became more complex with moulded mullions, tracery made of wood and deep projecting cills. The glazing was increasingly laid within rebated frames and secured with 'glazing sprigs' rather than being inserted into lead cames. This method of glazing is not only less prone to leaks but also allows for larger clearer, more transparent sheets of glass to be used in the windows than would be possible without the need for lead lights.
Energy efficiency
Traditional timber windows are energy efficient due to their thickness, multilayer construction and attention to the smallest of details. The large glass areas, the deep projecting cills, and the large glazing areas help to reduce air infiltration. With secondary glazing and draughtproofing the windows can be improved to increase their energy efficiency. It is important to remember that these measures should be considered in relation to the overall integrity and look of the original windows.
It makes sense to fix or upgrade windows, rather than sash windows cambridge replacing them, particularly when improvements in energy efficiency can be made by simple repairs. The windows of the past often have a historical value that demonstrates a range of technological advances and changes in architectural taste. The pressures to replace these windows are generally based on the assumption that the windows of the past will require replacement in the near future, but they are capable of serving for 150, 200 or even 250 years if they are properly maintained.
It is essential to understand that the decay issues caused by traditional windows made of timber can be avoided by regular maintenance and prompt repairs. In addition it is vital to spot damp penetration issues and fix them promptly to prevent serious damage. The early deterioration of paint is a particular problem, as it allows moisture to penetrate the wood and cause wet rot. It is not uncommon for this issue to go unnoticed until the paintwork starts to crack or turn wavier. However, it could cause structural damage and lead to further decay.
A quality paint will prevent moisture penetration. To prevent mould and condensation it is essential to keep the paintwork as clean as you can. The use of modern synthetic paints could be a problem because they are usually formulated to be water-resistant, which can cause the growth of mildew in the window frame.
The majority of windows from the past were constructed from timber with an extensive proportion of sapwood. The timbers will deteriorate quickly when exposed to moist weather, but can be protected with an extensive preservative treatment prior to when they are used. It is also essential to ensure that the kind of timber used is well-suited to the location and climate conditions, as these factors will influence the durability of the joinery. Local window manufacturers make a variety of timber sash that can be adapted to fit specific openings from the past. They can be made in the standard Boston pattern or in custom sizes to fit historical structures.
Maintenance
The life of timber windows can be extended significantly through regular inspections as well as a careful redecoration and timely repair. The most common reason for the decay is the infiltration of moisture through the deterioration of paint and putty. This can be prevented by using a good wood preservative and painting the wood thoroughly.
Repairs to sash windows that are old and window frames made of casement should be handled with care and minimal disruption. Repairs can be made to several traditional designs of timber windows without having to remove the frame. This should be done as often as is feasible. Remove any peeling or loose paint and lightly sand the area to improve the 'key" of the surface. This will enable the new coating to stick better. It is essential to not remove old paint layers, which may have historical value.
If a piece of timber is rotten, the best way to proceed is to remove the rotted material and replace it with spliced-in inserts that are shaped to fit the existing profiles. The timber that is inserted should be treated with a wood preservative. The junction between masonry sub-cill and timber cill should be sealed.
Replacement of traditional windows using PVC-u may be an appealing option, particularly when the installer offers an "all-in-one" installation that handles removal and replacement in a day. It is, however, essential that the person installing replacement windows has a complete knowledge of the structure and history of traditional wooden frames. This will allow them to make the appropriate recommendations for energy efficiency improvements as well as other technological improvements that don't alter the appearance of a historic building. Those providing replacement windows should be registered with a Competent Persons Scheme such as FENSA. This will ensure that the replacements are deemed as a suitable option under Building Regulations. It is, of course, possible for an experienced and skilled carpenter to install PVC-U windows that are sympathetic to the style of the building originally. This is particularly applicable when windows are in conservation areas or listed buildings.