Repair Dry-rotted Wood by Packing It with Polyester Resin Wood Filler or Patching It with a Wooden Block

Fix dry-rotted wood and make something old new again to preserve its character and save money. Restore the appearance of dry-rotted shutters, window frames and other non-weight bearing surfaces by patching with a wooden block or forming three-dimensional reconstructions with polyester resin wood filler. A utility knife, sandpaper and paint complete these DIY projects, but neatness counts!

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brushing wood hardener onto the dry rot
Step 1

Remove Crumbling Dry Rot and Apply Wood Hardener to Remainder

Remove crumbling wood and apply an epoxy-like wood hardener to consolidate the remaining affected area. Brush on the water-thinned wood hardener liberally so that it soaks into the rotted areas. Let it dry for about two hours.

taping the form in place
Step 2

Build a Form around the Damage to Shape Wood Filler

Build a form around the damaged area with pieces of wood/hardboard prior to packing the hole with wood filler. Spray lubricant on the form components to promote quick release from the wood filler. Tape or clamp the forms in place.

shaping wood filler edges with a utility knife
Step 3

Remove the Forms and Shape the Hardened Wood Filler

Allow the wood filler to dry for 10 minutes until it is hard and rubbery. Detach the forms and remove excess material with a utility knife, wood file, and/or sand paper to shape and smooth the repair.

tracing a cutline for a wooden block patch
Step 4

Repair Broken out Areas with a Wooden Block Patch

Cut a slightly over-sized block to fit the damaged area, trace it and cut on the trace lines with a Japanese handsaw to remove the dry rotted edges. Use a chisel or other hand tool to fit corners.

securing a one-handed face-frame clamp to hold the block
Step 5

Apply Glue and Clamp the Wooden Block Patch in Place

Glue the block into the shaped dry-rot damaged area with polyurethane glue. Position the block with a one-handed face-frame clamp to hold it horizontally and vertically until dry. Sand the block's surface flush with the surrounding area.

painting to dress and weatherproof the repaired dry rot
Step 6

Paint the Sanded and Repaired Surface with Exterior Paint

Smooth the edges of the filled or block-patched repairs and other surface imperfections prior to applying two coats of good quality exterior paint. The paint will weatherproof and dress the repairs and extend the life of your repair project.

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