To build a shower stall, remove the room's existing walls and prepare the shower's framework by digging a foundation. Install a drain and fill the foundation around that drain with cement. Smooth the cement and add a waterproof sealant. Lay tiles if desired. To lay tiles, measure the foundation and calculate the number of tiles needed. Tile the base first then the walls. Apply grout to the tiles. Install a door sill and frame then panel the shower door frame.
When removing the walls, expose the wall's wooden framework including the studs. Check where the hot and cold water lines are in the wall to make sure they can reach the shower head. Insulate the hot water pipes and shower walls by placing insulation between the studs. With cement adhesive, fasten cement boards over the studs and insulation to create the shower walls. If you cannot dig a shower foundation, use lumber to build an elevated base and curb to set the shower apart from the floor and create the shower floor slope necessary for proper drainage.
When adding cement to the foundation, slope the cement inwards so water moves towards the drain. Spread a layer of thinset mortar over the cement boards and cement floor to act as an adhesive for the tiles. Allow the tiles to dry and set for 24 to 48 hours. Dampen the tiles with clean water before applying grout.
Glue the desired door sill to the curb of the shower. Allow the sill several hours to properly adhere to the curb, then seal the joints. Install the shower door frame by sliding it into place on the sill. Apply caulk to any gaps to seal the shower and prevent water from escaping.