How to Repair Fiber Cement Siding
Step 1: Clean the Split Boards with Wood Surface Cleaner
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 skin and eyes.
Step 2: 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 shinglers, 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 crack.
Step 3: Repair the Crack in the siding Board
Sand both edges of the crack with 120-grit paper so they are fairly smooth and free from splinters. This will helpsthe adhesive form a tight join. 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.
Step 4: lnspect and Sand the Repaired Boards
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.
Step 5: Reattach the Repaired Board to the Exterior
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.
Step 6: 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.completely acrylic paint, and apply with rollers. Depending on the size of your house, you may need a ladder to reach the area of siding near the roof. Remember, above all else, that you must not stain siding; the material is not able to hold the stain, and the end result will not be pretty! Only use paint.
Selected from: https://www.doityourself.com/stry/cedar-siding-repair-how-to-repair-split-boards
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