Cedar Siding Repair: How to Repair Split Boards

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What You'll Need
Wood surface cleaner
Scrub brush with nylon bristles
Wood putty
Waterproof wood adhesive
Putty knife
120 and 200-grit sandpaper
Pry bar
Nail ripper
Hacksaw or power blade saw
Wood clamps
Claw hammer
Galvanized nails
Penetrating wood stain
Large paint brush with nylon bristles
Eye goggles and work gloves

Many reasons may necessitate cedar siding repair on your home. The main reason cedar siding boards can split and crack is moisture in boards subjected to extremes of hot and cold weather. Use the steps outlined below to repair and reattach split cedar siding boards.

Clean the Split Boards

Remove dried wood and splinters from the split boards with wood surface cleaner. Soak the wood thoroughly with a garden hose and apply the wood surface cleaner in the correct concentration according to the label directions. Use a scrub brush with tough nylon bristles to get all the grayed and dried wood flakes off the exterior. Scrub until you can see healthy, pinkish-red cedar on the surface of the boards. Wear eye goggles and work gloves when using wood surface cleaner, as it contains strong chemicals that can harm your skin and eyes.

Remove the Cracked Boards

Using the pry bar, lift up the board until you can see the nail shafts. Pull the nails out with a nail ripper, used by roofers, or cut through the nails with a hacksaw or power saw. Hammer the remainder of the nails out of the board by striking the nail shafts upward. Pull the boards out carefully and inspect them to see if you can repair the cracks.

Repair the Cracks

Sand both edges of the crack with 120-grit paper so they are fairly smooth and free from splinters. This will help the adhesive form a tight joint. Fill the edges of the crack with wood adhesive and the center with wood putty. Pack the wood putty in tightly with the putty knife. Clamp the board to ensure it retains the putty. Repair small perforations and cracks in the boards with the wood putty at the same time. Leave the puttied sections of the boards to dry for 24 hours in a location where they will not get damp.

Inspect and Sand

The next day, check that the cracks, splits, and perforations are fixed, and the boards are solid enough to reuse. Sand off any excess putty and adhesive from the board surface with 200-grit sandpaper.

Reattach the Repaired Boards

Replace the siding boards one at a time on the exterior. Hammer them into place with anti-corrosive nails that have been galvanized or dipped in hot liquid zinc.

Refinish the Siding

If just the repaired portion needs refinishing, apply a deep penetrating wood stain in the color of your choice. Avoid polyurethane finishes as they can trap moisture below the surface of cedar. If the entire exterior needs to be refinished, wash all the siding down with wood surface cleaner. Allow the siding to dry for at least 12 hours, and reapply your preferred weather-resistant wood stain.