How to repair a rotten window frame

Updated April 17, 2017

Dealing with rotted wood is something most homeowners must face at one time or another. Water is wood's biggest enemy, and window frames seem to be particularly susceptible to wood rot. There is an easy way to repair your rotted wood window frames permanently, allowing you to restore your pride of home ownership as well as your home's exterior beauty. Epoxy is the best choice when it comes to repairing rotted wood, and it's pretty simple to use.

Clean and prep the area you're repairing. Use a chisel and hammer to chip away as much rotted wood as you can (rotted wood will be soft and moist). Wear safety glasses as you are gouging out the rotted wood. Make sure the remaining area (the area you're going to repair) is dry before you apply the epoxy.

Drill 6mm (1/4-inch) holes around the area you're repairing. The drill holes should be about 13mm (1/2 inch) apart. Drill deep, but don't drill all the way through the wood. These holes will let moisture escape.

Tent the area you've just cleaned and prepped with loose fitting plastic. This protects the area of repair from moisture. Let the area dry about a week.

Brush on wood consolidant. You don't have to let it dry before continuing the repair; you can begin application as soon as you've mixed the epoxy.

Mix equal parts of parts A and B of the epoxy wood filler by dipping into each part with a stir stick and ladling golf ball-sized portions onto a piece of scrap board. Stir the two parts with a putty knife for about 3 minutes.

Spread a layer of the mixed epoxy into the area of repair with the putty knife. Work it in with your fingers (wear rubber gloves). Put enough epoxy in so you can shape it to match the rest of the frame. You may need to apply several layers of epoxy to fill the space. Let dry (drying time will range from 3 to 24 hours, depending on the temperature).

Shape the epoxy with a file and 80-grit sandpaper to match the existing window frame once the epoxy has hardened. To see if the epoxy has hardened, try pushing your fingernail into the epoxy. If it doesn't leave an imprint, the epoxy is hard.

Rough up the surface of the epoxy with 120-grit sandpaper, tape off the glass around the window frame and then paint. You may want to repaint the entire window frame to make sure the painted surface is seamless.


If you accidentally drill through the wood, patch the bottom of the hole with wood putty.

After you've tented the area of repair and let it dry for a week, uncover and continue the repairs on a dry, sunny day.

Temperatures make a difference when working with epoxy. Heat accelerates the hardening of the epoxy; cold slows it. If possible, work in the shade and keep the epoxy cool at about 21 degrees C (70 degrees F).

You can cut blocks of wood to fill large or deep areas of repair and glue it to the window frame with the epoxy. Use the same kind of wood and line the grain in the same direction as the existing wood in the frame.

If you need to thin the epoxy, add a little wood consolidator.


Wear safety glasses when drilling and sanding. Wear chemical-resistant gloves when handling the epoxy.

Things You'll Need

  • Hammer
  • Wood chisel
  • Safety glasses
  • Power drill
  • 6mm (1/4-inch) drill bit
  • Wood putty
  • Wood epoxy, parts A and B
  • Wood consolidant
  • 2 paintbrushes
  • Putty knife
  • Scrap piece of board
  • Stir sticks
  • Chemical-resistant gloves
  • Metal file
  • Sandpaper, 80- and 120-grit
  • Painter's tape
  • Exterior paint to match the existing frame
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About the Author

Based in California, Tracie Grimes began writing in the medical field in 1984. She has since expanded her areas of expertise to include DIY projects, parenting and craft articles. She is a monthly contributor to "Kern County Family Magazine" and "Bakersfield Magazine," with work also appearing in parenting magazines across the United States. Grimes received her bachelor's degree in journalism from Northern Arizona University.