How to Rebuild Wooden Windowsills

Question: Recently my daughter visited with her puppy, which promptly gnawed off part of two wooden windowsills in the bedroom. How can I repair these without replacing the whole sill? They are wood with a stain finish.

Answer: Sometimes the easiest and most cost-effective means of repair is to replace the damaged material. This is usually the case if the damage is extensive and the material in question can be easily replaced. Removing a wood windowsill can be a major undertaking, so we suggest that you try rebuilding it with an epoxy or two-part wood filler.

The fact that the windowsill is stained rather than painted makes the repair task a touch more challenging, but it still can be accomplished with a bit of patience. Start by using a file and sandpaper to remove loose material. The surface must be clean, dry and free of grease and oil. Use a small drill bit (3/32 or so) to drill multiple holes in the face of the damaged windowsill. The holes will help the wood filler bond to the wood.

Mix the two parts (filler and hardener) according to directions and immediately apply the paste to the repair area using a putty knife. Apply more material than is needed and use the putty knife to tool the material to match the profile of the windowsill. You’ll need to work quickly because the filler will be workable for only 10 minutes.

After 20 to 30 minutes, the repair will be sufficiently hard for you to be able to finish shaping the profile using a sharp modeling knife, plane, file and sandpaper. Because wood fillers can’t be stained, we suggest that you use paint to “faux finish” the repaired area to blend in with the existing stain.

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For tips, visit the Carey brothers’ Web site at https://www.onthehouse.com.