How to Repair Rotten Weatherboards

Remove the damaged weatherboarding, as well as any undamaged weatherboarding surrounding the affected area. Apply gentle pressure to the seams between the weatherboards using a crowbar until the nails loosen. Discard the damaged weatherboarding. Remove the nails from the undamaged weatherboards and set them to the side.

Examine the area behind the weatherboards for water damage. If there appears to be warping, heavy discoloration or extensive rot or mold, consult with a professional before proceeding.

Lay the damaged weatherboard on top of a new piece of weatherboarding. Use a pencil to mark the edge lines of the damaged weatherboard onto the new piece.

Cut the new weatherboard to length, using a circular saw.

Locate the studs in the damaged section of the wall, using a stud finder. Mark the edges of each stud with a pencil.

Reinstall the weatherboarding. Work from the bottom piece up toward the top, nailing each piece of weatherboard at the top of the strip using a hammer and 3/4-inch nails. Drive your nails into the marked studs to ensure a secure installation. If there is weatherboarding still in place above the damaged area of the wall, you might need to loosen it slightly in order to slot the lower pieces back into place.

Seal all seams around the new weatherboarding with a high-quality, clear silicone caulk. Allow the caulk to dry thoroughly.