To install a new bathroom, you need an extra-wide ‘wet wall’ built of two-by-six or two side-by-side two-by-four walls. Unless you live in a warm climate, do not run pipes in an exterior wall. Make sure your framing accommodates the tub.
Set the shower base by making sure the drain is directly below the opening of the base. Cement an extension to the drainpipe, ensuring it is flush with the floor.
Fit the rubber flange that is provided with the shower over the drain extension using liquid soap as a lubricant and push it far down. Tap it in place using a ¼-inch steel rod and install the drain strainer.
Then, build two-by-four walls for the sides. Do not place the studs more than 16 inches apart. On the plumbing wall, space the studs to allow the placement of the shower faucet, and install horizontal braces to support the showerhead arm and the faucet. Install the faucet and supply pipes.
Cover wood surfaces with backer board and attach the board to the studs with backer board screws. Use ceramic tiles to cover the backer board. Allow the adhesive to set overnight.
Stir a batch of latex-reinforced grout and push into the joints with a grout float. Scrape away most of the excess before wiping with a damp sponge to create consistent grout lines. Caulk all the inside corners.