Notes

7 Things You've Never Learned About Cambridge Window
Maintaining Timber Windows

A well-maintained timber window is a significant element of the historic structure of a building. It illustrates in varying degrees the different materials and technologies design, craftsmanship and aesthetics of the time period from which it dates.

If possible, repairs should be done in-situ. Proprietary resin-based repair systems can be used to fix the most damaged areas of decay without removing the whole window.

Durability

The timber windows in many historical structures were designed to last for a long time. However, they need to be maintained to ensure that they look good and operating properly. Maintenance tasks include repairs to sash cables and retightening pulleys for sash and painting. The need to upgrade timber windows in order to increase energy efficiency is also growing. This can include replacing old glazing units, fixing existing window rebates or installing new cills to improve air seal.

One of the major issues with traditional windows is damage caused by the corrosion of the paintwork. This is especially important where sash windows are involved as the gaps between sashes can be extremely large. In these instances water can enter the paint film and cause rotting to the wood or putty beneath. Poor weather conditions can exacerbate the decay. To stop this from happening, windows should be regularly painted with an exterior wood paint.

Areas that have been damaged must be repaired using resin-based products. This will ensure that the greatest amount of original fabric is preserved. It is important to minimize the number of holes that are drilled into the frame in order to allow cable access, as these can admit moisture and cause decay.

Another major issue 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 the sash not fitting properly, sticking or jamming in the opening and broken glazing. This can often be fixed by the fitting of new sash boxes constructed from slow-growing deal (pine) or oak. The cill must be made of a strong hardwood such as oak, to prevent shifting between the new and older work.

There are now several companies that manufacture Boston pattern wooden sash to fit most existing openings. They are available in a range of sizes and finishes to meet the needs of today's homeowner. These new sash, when combined with quadruple draft strips and improved thermal insulation can make a significant difference to the efficiency of a home's energy use.

Aesthetics

A lot of old timber frames have a high aesthetic appeal, as they reflect, in some form, the quality of the wood technology, the construction process, and the architectural aesthetics of the time they were built. They could have significant historical value as a set. This is especially true of windows that were unglazed in the early days of timber-framed structures, where the great majority were simply a series of openings within the frame that were subdivided horizontally into mullions and wood or iron bars to deter invaders.

It is essential to preserve the appearance of traditional timber window joinery. It is essential that any decay that results from the penetration of moisture should be stopped as soon as it is recognised. It is recommended to do this with thorough painting, particularly if there is damage or degradation. It is best to use paints 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.

The fungus that causes wet rot can spread quickly in old windows made of wood. To stop cambridge windows and doors from happening, take out any damaged or rotten parts as promptly as you are able to. The replacement of wood that is rotting must be done with care using slow grown deal (pine) and, if feasible it is the same species as that which is being removed to avoid any movement differences between the new section and the existing timbers.

In the late period of the 17th century and the middle of the medieval period, glass became cheaper and more abundant, and the openings for glazed glass in timber-framed buildings gradually became more sophisticated, with tracery made of wood, moulded mullions and deep projection cills. The glazing was increasingly placed within frames with rebates and pinned in with 'glazing sprigs' rather than being inserted into lead cames. This method of glazing not only makes windows less likely to leak, but also allows for wider sheets of clearer glass to be utilized than would have been possible without the use of leaded lights.

Energy efficiency

Traditional timber windows provide an excellent energy performance due to their thickness, multi-layer construction and very careful attention to detailing. They also feature large glass areas and projection cills which reduce air infiltration. With secondary glazing and draught proofing, 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 appearance and integrity of the original windows.

Therefore, keeping existing historic windows that require repair rather than replacing them makes sense particularly when thermal enhancements can be made economically through simple repairs and improvements. Older windows are usually of historical significance, since they show a range in technological advancement and changes in the architectural style. Many people believe that these windows will have to be replaced in the near future. However, most can still provide service for 150, 200, or even 250 years if you take care of maintenance.

It is important to recognise that the decay problems that are typical of windows made of timber can be avoided by thorough maintenance and timely repairs. It is also important to identify damp problems and correct them swiftly to avoid major damage. The early deterioration of paint is a major problem because it allows moisture to penetrate the wood and cause wet rot. It is not uncommon for this type of damage to go undetected until the paintwork begins to crack or become wavier. However, it can cause structural damage and lead to further decay.

A good quality paint will prevent this moisture penetration. To avoid condensation and mould it is crucial to keep the paintwork as clean as you can. The use of modern synthetic paints can be problematic because they are usually made to be water-resistant and this can result in the formation of mildew in the window frame.

The majority of older windows were made from timber that contained a high proportion of sapwood. The timbers will deteriorate rapidly if exposed to rain, but they can be protected by a thorough preservation treatment before use. It is also crucial to ensure that the kind of wood used is suited to the climate and site conditions, as these factors can affect the longevity of the joinery. Local window manufacturers create a range of sash made of timber that can be customized to fit specific openings in historic buildings. They can be produced in the standard Boston pattern or in custom sizes to suit historic buildings.

Maintenance

The lifespan of windows made of timber can be extended considerably through regular inspections, careful redecoration and timely repair. The primary cause of wood decay is moisture leaking through deteriorated paint and putty. This can be prevented by using a quality wood preservative and thoroughly painting the wood.


It is important that repairs to old sash or casement windows are properly executed and done with the minimum disturbance. It is possible to repair several traditional designs of timber windows without removing the frame. This is a must whenever it is possible. Peeling or loose paint must be removed with care and sanded lightly to improve the 'key' of the surface and facilitate a better adhesion of the new coating. Be careful to avoid stripping paint layers that may have historic value If these are present, it is recommended that a paint analysis be carried out.

When a piece of wood has become rotten the best course of action is to take out the rotten material and replace it with spliced-in timber inserts that are shaped to match existing profiles. The wood that is inserted should be treated with a wood preservative, and the junction between the timber cill and the masonry sub-cill should be sealed.

Replacement of windows made of traditional PVC-u may be a tempting option, especially when the installer offers an "all-in-one" installation that takes care of removal and replacement within one day. It is crucial that installers of replacement windows are aware of the history and construction of traditional timber frames. This will allow them to make appropriate recommendations for energy-efficiency improvements and other technological advancements that won't alter the appearance of an historic building. Anyone who installs replacement windows should be registered with a Competent Persons Scheme such as FENSA. This will ensure that the replacements are approved as a suitable option under Building Regulations. It is certainly possible for an experienced and skilled carpenter to install PVC-u windows that are sympathetic to the the original building. This is particularly true where the windows are located in listed buildings or conservation areas.

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