An exterior door that doesn’t have a coating of paint or other protection may eventually begin to show signs of rot. It’s important to remove rotted wood on exterior doors as soon as you notice a problem, so you can protect the integrity of the door. Epoxy wood filler works well to repair a door with rotted wood. The epoxy is easy to mold to fit the damaged area and you can sand it to a finish that resembles that of the door. You can complete the repair process using basic tools you probably already own.
Slide the hinge pins out of the door’s hinges. Set the door on a flat work surface with the damaged side facing up.
Scrape away any loose paint with a putty knife or paint scraper to make it easier to see where you need to make the repairs. Poke around on the surface of the exterior door, using a sharp object like an awl or screwdriver, to identify where the wood has rotted. Pull off any damaged wood that you can to make the repair easier.
Drill a series of 1/4-inch holes into, but not through, the door across the damaged area. Space the holes about 1 inch apart.
Mix two-part wood hardener, according to package directions, in a small squeeze bottle that has a nozzle small enough to fit into the 1/4-inch holes. Squeeze the wood hardener into the holes you drilled. Use a small paintbrush to spread the hardener across the damaged open areas. Saturate the wood that needs repair with the hardener. Its purpose is to consolidate and seal the wood fibers together and to help prevent any further water damage or rot. Allow the hardener to dry. This may take as long as seven days, depending on the product you select. Cover the door with plastic sheeting to keep it dry during rain showers if you are doing the work in an uncovered area.
Put on chemical-resistant gloves. If you are working indoors, put on a face mask as well. Open the windows.
Label two stirring sticks as A and B. Put stick A in the epoxy resin. Label the resin with a corresponding A. Put stick B in the epoxy hardener. Label the hardener B. Do not let stick A touch the hardener or stick B touch the resin.
Place a golf-ball sized piece of epoxy resin on a piece of scrap plywood with stick A. Put A back into the can. Put an equal amount of hardener beside the first amount with stick B. Put B back into its can. Use a separate stirring stick to mix the two pieces of epoxy together.
Push the epoxy wood filler into the holes you drilled into the door using a putty knife. Smooth additional wood filler into any open areas on the exterior door. It’s better to have too much filler in the holes at this point than not enough. Allow the filler to harden four hours or overnight.
Sand the exterior door by hand with medium-grit sandpaper to remove excess wood filler. Once you remove the excess, go over the door again with fine-grit sandpaper to smooth the wood to the same texture as the original wood.
Prime the door with a coat of exterior primer. Allow it to dry. Give the door two coats of paint, allowing each coat to dry thoroughly before proceeding. Rehang the door.