Shower board is the general name given to a host of products that are used beneath a shower's tile. The most common is cement backer board. Extruded plywood and fibreglass boards are also commonly used. Installing each requires a little diversity in skill and some patience. Cement backer board protects walls from rot by resisting water intrusion. You must be certain your wall frame boards are perfectly straight and flat before the installation.
Check the frame boards to ensure they are level and flat using a carpenter's level. Measure the width of the first wall.
Cut the cement board to this width. First mark the board with a ruler at both ends to the width. Line up a drywall ruler to the marks and score the cement board with a razor knife along the ruler. Crack the board along the score line by hand.
Place the board on the wall frames in the shower area. Drill pilot holes through the board and into the studs. Measure 16 inches from the end of the wall or the first stud to locate the position of the stud frame boards. You can also locate them with a stud finder. Mount the boards to the wall with concrete screws and a power driver.
Measure and cut the next section of shower board using a tape measure, the pencil and drywall ruler as you did before. Set this board 1/8 inch from the previous board. Mount it as described above.
Caulk the gap between the two boards with a continuous bead of silicone caulking material.
Continue to measure, cut and install the shower board until the entire area is covered. Caulk the edges of the finished installation with silicone.
If you choose to nail the shower board to the wall, use galvanised or corrosion-resistant nails.