Windows on historic buildings are an important mark of the architectural character. While this is obvious for decorative or stained glass windows, it can be equally true for buildings with historic wood windows. We always recommend keeping and repairing the original windows whenever possible. The repair of historic wood windows is more practical than most people realize, and many windows are replaced because of a lack of awareness of repair and maintenance techniques.
It’s very common for historic wood windows to start having issues when there is a lack of maintenance. Good news is that identifying and managing the problem can be a simple maintenance task.
There are several factors that can affect wood windows. Here are some signs to look for when inspecting your windows:
- Is your window looking ‘not so square’ anymore? This could be evidence of structural movement which is deforming the opening and damaging the window. Keep in mind that some signs of movement may be so old that they have stabilized or repaired, leaving the window in working order.
- Is the seal between the window frame and the wall opening cracked, loose, or missing? These gaps allow water and drafts to get in around/behind the window frame.
- Is the window sash (frame) stuck or doesn’t move right? This may be due to:
- paint buildup over the window joints.
- window pulley wheels that have seized up because of over-painting or lack of lubrication.
- broken sash cords.
- swelling due to water absorption (see below).
- thicker and heavier replacement glass.
- failure of hinges on casement sashes.
- Evidence of water absorption, indicating possible wood decay (wet rot). The signs to look for are:
- interior paint failure caused by condensation.
- exterior paint failure.
- opening of the frame joints.
- deterioration of the wood surfaces (where paint has flaked off) or depressions in the wood surface.
- cracked, loose, or missing putty.
- standing water, especially on the sills.
- Faults with flashings or water shedding features associated with windows.
In order to fix the problem, you need to identify the nature and causes of defects so that the correct treatments can be selected.
- Keep the exterior surfaces painted, including the glazing putty. Paint protects the wood and putty from water and extends their service life. Be especially attentive to horizontal surfaces where water may collect.
- Glazing putty will eventually dry out and is meant to be periodically replaced. You can do spot repairs initially, but eventually it will be easier to reglaze the whole sash.
- Keep movable surfaces, such as the inside jamb, free of paint build-up so that the sash can slide freely.
- If your sashes are hung with cord, keep the rope free of paint. This will improve the window’s operation. Cord will eventually dry out and break but can be replaced. When replacing the cord you can also re-hang the weights so that the sash will be balanced.
It is important to ensure that water does not enter crucial joints, such as in the lower parts of sills or jambs, where deterioration most often occurs. Joints should be kept tightly closed. In addition, it is helpful to seal end grains with paint before assembly. You should also keep an eye out for any putty failure (which encourages water to sit on the horizontal surfaces of the glazing bars and meeting rails) and for deterioration in the protective paint finish.
We want you to be able to keep your historic wood windows for many, many years to come! Have you repaired your wood windows? Tell us your experience on Facebook, Instagram, or Twitter. We’re here to answer questions and celebrate your successes with you!
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