Wooden windows frames and sills provide a homey, warm look to a home. They are also quite common in older homes that did not have option of choosing vinyl windows at the time. A common problem with wooden windows is that they can develop dry rot if they are not maintained properly. Fortunately, sometimes dry rot can be repaired, and if you are careful, you can prevent it from spreading or coming back in the future.
Take action against rot as soon as you notice it.
You should make it a seasonal task to inspect the exterior frames of your windows to make sure rot hasn't taken hold. Once rot has set in, it can spread very quickly, necessitating the replacement of the window, instead of a simple and less costly window repair. Signs of rot include warping, splintering, cracking, visible mold, or peeling paint. Rot is more common when windows are exposed to moist conditions for a long time, which penetrates the sealing caulk and paint that would normally keep the windows safe.
Repair the rotten section.
If you are fortunate enough to catch the onset of rot on your window, you can begin repairs by removing the portion of the window that has fallen victim to decay. Infected wood will have discoloration and warping, peeling away easily, while healthy wood will remain dry and firm. You can gouge out the rotten portion carefully using a hammer and chisel. Remove all the rotten portions until you get to clean, dry wood.
Note: Because rotten sections must be removed to make this repair, windows that are completely given over to rot, or even have a significant amount, will not be able to repaired in this way. Replacement is the only option in these circumstances.
After you have removed the rot, it's time to fill the area back in again. Begin by using a thin drill bit to make several holes in the healthy wood-- use two fingers to space them out, and don't drill them too close to the edge, as this can weaken the frame. The holes help the wood filler used to repair the frame have a strong adhesion to the existing window. The holes will be filled first and become the anchor for the rest of the filler.
Next, use an epoxy consolidant to seal the gouged-out areas. You should start with a thin layer to fill the prep holes partially, and seal the surface of the healthy wood. The wood, you will notice, will absorb the first coast slightly-- this is a good thing, as it will protect against future rot. Use a second coat on top of the first coat for added protection.
Then, the area is ready to be filled with epoxy wood repair filler. The filler may be quite thick, so you should use putty knife and chisel to help form it perfectly into the gaps. Shape it as best as possible with the existing wood frame. Allow the filler to dry per the manufacturer's instructions. Once the filler is dry, you will sand it down to help it blend uniformly with the rest of the window frame.
Paint and prevent future problems.
The window frame is finally ready for a new coat of oil-based exterior paint. The paint provides the defense against future problems with rot. If you notice the paint is peeling around other areas of the frame, consider sanding off the old paint before putting on a new coat, as the sanding will help the new coat provide a better seal.
To prevent problems with rot in the future, you need to make sure that your windows are properly cared for. Repainting wood frames every few years, as well having the gutters on the roof in good working order, will help to make this repair process a one-time project.