How to Join Strips for Lap Siding

Prime all of your siding pieces on all sides before installation. This protects the full lap siding material from rot. Only do this if you plan on painting your siding.

Strip the walls of any previous siding. Cover the site with a code-approved building paper or a roofing felt. Keep the surface smooth, so the siding can easily follow along the contours. Cover all the surfaces with the building paper, even under all the trim pieces.

Install a self-stick flashing or metal flashing before you apply the trim to ensure that water will not infiltrate the wall.

Make the necessary measurements around the eaves, curvatures and windows. Determine the desired "reveal," or the vertical width that is exposed to the outside. For the easiest application, purchase shiplapped or bevel-rabbeted siding, as the reveal is determined by the manufacturer and will remain consistent over the entire application.

Mark level lines the full distance around the house to ensure a clean and professional look. Make sure the last boards meet at the same level. Chalk a line to indicate the top of the bottom board. Cut your board to fit tightly in its designated spot. Align the board with the chalk mark line, then drive nails into the upper flap that will be covered by the lap overlay above it, every 6 inches for the starter strip.

Cut and align your second lap board with the bottom piece, so it is aligns with your previous measurements. Use a level to verify that it is straight and that your marks are correct. This second board should lap perfectly over the first piece and cover all the nails.

Cut the boards so they meet in the middle of a stud to create a butt joint. A solid butt joint will make a seam tight and not obvious. Test the boards together to verify that the fit is snug. Add caulk to both board ends to secure the seam. Drill in several pilot holes before you nail the boards to the house.