Tom Shafer

Fix wood rot: save your window frame

June 01, 2012

It's spring and time to paint some of your wooden windows. As your paint brush passes over the sill, you notice some of the wood is soft. Can you ignore it? Better not.

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If your finger pokes through the wood as you investigate, you will need to repair wood window frames before painting them -- or buy replacement windows. If you're thinking you can replace the window sill and call it done, trust me; it's not that easy. Why not fix wood rot in just the deteriorated section?

How to temporarily repair rotted wood

It's not possible to permanently patch rotted wood, but you can fix wood rot temporarily. It is my experience that once rot starts, it cannot be stopped. Eventually the infected section will have to be replaced. Until you can get replacement windows -- perhaps in a material that, unlike wood, doesn't rot -- following these four steps can help you repair wood window frame rot for the short term:

  1. With a chisel and a knife, cut and scrape all of the soft, rotted wood out. Make the area as clean as possible; use a paint brush to sweep all dust and wood particles out of the hole. Make sure that the area is dry and as dust-free as possible. If deteriorated material is left, the repair cannot last long: The rotting will continue.
  2. Using a wood hardener such as one made by Elmer's, saturate the wood in the hole you've scraped out, and let the hardener set. The hardener is needed to insulate your repair material from the remaining softened wood.
  3. Apply a two-part, epoxy resin -- Elmer's and Minwax are two popular brands. Mix the resin, then use a putty knife to push the mixed resin tightly into the hole. Assure that it is smooth and flush with the surface. It can sink and contract as it cures, so a second coat may be necessary. Bondo is a less expensive alternative than the epoxy resin -- it's the two-part resin used for auto body repairs, and it also works well for repairing wood rot.
  4. When the resin is set and hardened completely, sand the repair smooth with the surrounding area, then paint.

Horizontal areas are easier to repair because the repair material does not slide out. On vertical surfaces, a drier mix is needed. Sometimes it helps to make a dam out of tape to hold vertical repairs in place until the repair material hardens.

While this type of repair is not permanent, it can hold for as much as several years until the part that's rotted can be replaced or you're able to get new replacement windows.

About the Author

Tom Shafer has decades of experience in window sales, marketing and product development. He's worked closely with window design engineers in testing, design, and building code interpretation. Past employers include United Windows and Doors and Norandex, MI Windows. He currently works at a home improvement retailer.

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