Shiplap siding is a building material that protects the underlying structure of your house from water and sunlight damage. The individual boards that make up shiplap siding are designed to lock together tightly with one another to create a cohesive shell around the house. Repairing a damaged shiplap siding board involves first cutting the board in half lengthwise so that it can be removed from between the surrounding boards. After the board has been cut, it can be removed and replaced by a new piece of siding.
Use the circular saw to cut the damaged siding board in half along the length of the board. Adjust the saw blade so that it cuts to a depth matching the thickness of the siding board.
Pry the bisected board up with the pry bar. Slide the bar in near the nail holes and lift the split halves of the boards until the nail shafts are exposed.
Use a slater's ripper to pull the nails, or a hacksaw blade saw to cut the exposed nail shafts. A slater's ripper is a specialised tool that can be slid under the siding to hook and pull the nails. A hacksaw blade saw is a narrow, toothed saw blade mounted to a handle. The blade can be slid underneath the siding to sever the nail shafts.
Once you've got the nails pulled or cut, remove the two pieces of the siding board from the wall.
Use your circular saw to cut a new piece of shiplap siding to the proper length. Fit the piece into place, notching the top edge of the board underneath the overhanging bottom edge of the board above. Use a mallet to knock the board gently into place.
Fasten the board in place with corrosion-resistant nails. Don't overdrive siding nails. Follow the existing nail patterns to achieve a consistent appearance.