Dry rot occurs when wood is left wet for prolonged periods of time. The damp wood creates a favorable environment for fungus that eats away at the wood leaving it brittle and soft.
You can safe guard against dry rot through repairing and repainting cracked, chipped, or peeling paint, which are possible entry points for moisture and dry rot.
The first sign of dry rot is usually bubbling paint. If you insert a screw driver into the wood and find that the wood has become brittle and soft (almost foam-like), dry rot is present.
STEP 1: Drill, scrub, chisel, and/or wire-brush all dry rot out until hardwood is reached. Don't be gentle. Continually gouge the wood with a flat-head screw driver to test that you've reached hardwood. If all dry rot isn't removed, the fungi will continue eating away at the wood from within.
STEP 2: Next spray exposed wood with a dry rot killer or wood preservative. Allow it to soak in and gas off for several days. Don't rush it.
STEP 3: Brush on linseed oil to condition wood. Again allow several days for the wood to gas-off and absorb conditioner.
STEP 4: If dry rot damage is extensive, make forms with wood covered in wax paper. The wax paper will prevent the Bondo from sticking. Screw forms into hardwood around the empty spaces to be filled. Be sure to leave a gap to insert Bondo.
STEP 5: Mix small batches of Bondo and pack into forms. Let dry per package instructions and apply next layer until work area is filled. When dry, take off forms.
STEP 6: Shape and sand to match surrounding wood. Add extra Bondo with a putty knife to fill cracks and screw holes.
STEP 7: Calk, prime, and paint.
Regular inspection of wood and calk for cracks, chips, &/or peeling can prevent future damages.
flat-head screw driver
drill and screws
chisel and wire brush
wood preservative/dry rot killer
mixing container and stirring sticks