Things You'll Need
2-by pressure-treated lumber
1-by pressure-treated lumber
Automotive body repair putty
If you see a rotted rafter, you should take steps to identify the source of moisture that is causing the decay. This includes repairing any leaks in the roof above the rafter. It may also include replacing roof sheathing. Unless you have advanced carpentry skills, you may not be able to fix a rafter with serious decay problems. This type of repair affects the structural integrity of the entire roof. But if the decay is on the rafter tail above the house's soffit, a do-it-yourselfer can usually complete this type of rafter repair.
Fix a Rafter Tail
Remove the molding between the fascia and the side of the house, using a pry bar. Work carefully, so you can reattach the molding later.
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Pry off the rotten portion of the fascia. Avoid damaging fascia that is not rotten. Pull off the soffit material to expose the rafter tails.
Cut off the rotted rafter tail with a reciprocating saw. Cut a replacement board from 2-by pressure-treated lumber that is the same size and width as the rafter tail you just cut, using a circular saw. Cut a piece of 1-by pressure-treated lumber that is longer than the replacement board by 4 to 6 inches.
Clamp the longer board to the rafter along with the replacement rafter board, using wood clamps. Place several screws through the 1-by lumber and into the 2-by to secure the boards to the rafter.
Cut new soffit and fascia boards to fit. Secure them with several screws.
Coat the new soffit and fascia with primer. Take care to coat all exposed edges.
Replace the molding that you removed in Step 1. Paint the repaired soffit and fascia with two coats of paint, allowing the paint to dry between coats.
Minor Rafter Repairs
Dig out damaged wood from the rafter, using a sharp tool, such as a screwdriver.
Coat the hole with oil-based primer. Allow time for the primer to dry.
Fill the hole with automotive body repair putty. Smooth the top level with the rest of the rafter with a putty knife. Allow the putty to dry. Paint the patch, if desired.