ArcaMax

Replacing a damaged wooden windowsill involves carpentry work because it requires removing an integral part of the frame, which is difficult to do. But you can repair the sill more easily by rebuilding the damaged sill and then shaping and sanding it to conform with its original appearance.

We’ve used two products: a two-part wood filler and hardener from Minwax and a wood filler and stabilizer from Bondo. Both are available at hardware stores and home centers. The filler is designed to fill holes and gouges in the wood, and the hardener and stabilizer are formulated to strengthen and reinforce the decayed or rotting wood. When the repair area is dry, you sand and smooth the surface so it can be finished with a primer and paint to match the existing finish.

You can hire a handyman to rebuild a windowsill for $240, which includes labor and materials. You can buy the material for $65, do it yourself, and save 73% for your effort. To do the job yourself follow the manufacturer’s direction about applying the material and drying time required. First, prepare the surface by removing any dirt and loose paint with a wood scraper. Then use a putty knife or disposable bristle brush to apply the filler and let it dry. Then apply the hardener. When the repair work is dry, smooth the surface using a pad sander with sandpaper before finishing the surface with a primer and paint.

Pro Cost: $240 — DIY Cost: $65 — Pro time: 3.2
DIY Time: 5.0 — DIY Savings: $175 — Percent Saved: 73%

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©2025 Gene and Katie Hamilton. Distributed by Tribune Content Agency, LLC.