How to Replace Hardiboard

Insert the pry bar around the damaged hardiboard piece and pry outward so you can see the attachment nails. Be careful not to mar the undamaged boards.

Loosen the board just enough so you can access the nails. Insert your bar under the nails and pull upward until you remove the nail. Repeat for all the nails until the board is completely unattached.

Remove the damaged board carefully so it does not affect the surrounding planks. Look for signs of problems in adjacent sidings or in the underlying structure, such as the sheathing or flashing.

Select, measure and cut the replacement board to size. If you have a selection of replacement boards to choose from, and they are textured, select a replacement with a surface that matches the damaged board as closely as possible. This will make the repair less noticeable. As a measuring guide, use the missing area of siding on the wall as well as the dimensions of damaged board itself. Cutting hardiboard can produce a lot of dust, so do it outdoors and wear appropriate breathing and eye protection.

Prime all exposed parts of the replacement, if needed. Even if the hardiboard is already primed, you’ll need to apply primer on any edges that have been exposed through cutting. Though you can apply primer after installation, doing it before makes it easier to reach all the edges. Allow the primer to dry.

Apply a continuous thin bead of permanent flexible caulk along any edges where two boards meet. Because this will prevent any moisture from seeping into the edges, ensure there are no gaps. Allow the caulk to dry.

Finish off the surface of the hardiboard, if needed, with paint to match the coat on the undamaged siding.