Correct Way to Apply Wood Filler to Exterior Siding

Follow the directions on the wood filler for the conditions needed for its application. The optimum conditions for applying wood filler are a temperature over 55 degrees and low humidity.

Remove any loose pieces of wood from around the area being repaired using a utility knife. The wood filler works best if it is applied to solid wood that is not splintered or loose.

Spray the area being repaired with compressed air to remove particles of dirt and other debris. The less dirt there is, the better the wood filler will adhere to the wood.

Clean the area using an old tooth brush and spray lubricant. The petroleum in the lubricant will loosen dirt on the surface of the wood and help prepare it for the filler. Let the wood dry for 20 minutes before applying the filler.

Spread the wood filler into the affected area using a putty knife. Press the wood filler into the area so it completely fills it. Smooth the wood filler so it is flush with the surface of the siding around it. Let the filler dry according to the directions.

Sand the filler lightly with 150- to 200-grit sandpaper to remove any ridges before painting or staining.