Refer to manufacturer recommendations for products that are compatible with fiber cement.
How to repair a chip edge in cement fiber siding.
Repair or patching fiber cement board siding dents chips cracks and other minor surface damage in james hardie siding and trim products can be filled with cementitious patching compound.
Dip a soft bristle brush into the solution then scrub the cracked area of fiber cement siding to remove dirt and debris.
Mix a solution of 1 2 cup trisodium phosphate and 1 gallon of water.
Step 4 mix the quick setting cement using a margin trowel by adding 5 parts cement to 1 part quikrete acrylic fortifier until a lump free putty consistency is achieved.
Step 3 thoroughly rinse the repair area after cleaning.
Brush away any chipped paint small loose pieces of siding or anything else that mars the plane of the siding.
Put on a pair of rubber gloves.
If your repair includes the very bottom tier of siding add a spacer strip the thickness of your siding along the entire bottom edge to mimic the angle of your overlap.
To clean it start by taking a light wire brush and dipping it in a buck of water mixed with a cup of bleach and some dishwashing detergent.
Allow the patch to thoroughly dry and apply another thin layer of patching material if the first layer shrank during the drying process.
Scrub and clean the surface of the repair area with a stiff bristle brush.
Scrub away at any bits of mold mildew or stains keep in mind that tough persistent stains might just have to be painted over.
Use a plastic putty knife to apply the patching material to the damaged area filling in the area and shaping the patch to match the original contours of the siding.