If you wanted to patch the hole I’d probably just caulk it, but if you wanted it to set up hard, use a stick of jb weld or similar and shove the putty in the hole. Then you can drill a pilot hole in it once it’s hard.Click to see full answer. Thereof, how do you fill holes in Hardie board? The cement basis of the product dictates the use of thin-set mortar to properly repair cracks or holes. Step 1: For holes larger than 1/2-inch in diameter, use a carton knife or carbide-tipped tool to cut a V-shaped groove behind the edges of hole. Step 2: Use a clean, damp sponge to wipe down the area to be patched. Additionally, how do you fix Hardie board? How to Patch HardiePlank Brush away any chipped paint, small loose pieces of siding or anything else that mars the plane of the siding. Sand over the damaged area lightly but thoroughly with a medium-grit sandpaper to smooth any jagged edges and create an easy grip surface for the patch product. Moreover, how do you repair holes in fiber cement siding? 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. Allow the patch to thoroughly dry and apply another thin layer of patching material if the first layer shrank during the drying process.Can you sand Hardie plank?The good news is, Hardie siding is easy to repaint! Whether you’ve got a ColorPlus finish or custom paint on your existing Hardie siding, you don’t have to prime or sand the original finish. Most James Hardie siding is installed with colour matched caulking around windows and at corners.