The minimum dimensions for a transfer shower is 36-inch by 36-inch. A roll-in shower must have dimensions of 60-inch by 30-inch, which is the same size of a standard size tub. In order to be able to maneuver a wheelchair, the area must be at 54-inches by 54-inches. However, if you have enough space, a 60-inch by 60-inch shower area would make maneuvering even easier. If you plan on installing a pre-fabricated shower tray, you may want to take that into consideration when deciding on the shower dimensions.
Before you begin framing the shower, check the subfloor and the framing joists underneath the floor. Repair or remove damaged or structurally unsound floor components before you start. Make the subfloor about 1-1/2 to 2-inches lower than the subfloor for the rest of the bathroom. Use floor joists with a smaller width in this section. Use metal joist hangers. If you’re working on a concrete slab, break out the concrete and excavate to the appropriate depth. This will give you the base you need to finish the floor at the appropriate level with the ceramic floor tile.
Usually, 2-inch by 4-inch lumber is used to frame the handicap shower walls. You can also use 2-inch by 6-inch boards if you want to install more than 3-1/2 of fiberglass insulation or to accommodate pipes. Also, install wood blocks between the studs to provide reinforcement for grab bars, a shower or any other type of accessories. Place blocking 8-inches high from the floor for the shower base. Finish the walls with cement board, but install the bottom boards only after you put your shower base in place.
There are two ways to approach the shower tray: you can purchase a shower pan that is ADA compliance or you can build your own pan.
The pre-cast pan is the easiest route. The drain and the splash wall are already built into the one-piece unit; just follow the specifications for installing product. If you decide to build the shower base, install a waterproof membrane on the subfloor. Install the membrane on a 1-1/2 to 2-inch thick mortar bed sloped toward the drain. Check the codes, but usually a 1/8-inch slope per foot is adequate. Run the membrane about 8 inches up the sides of the shower wall under the cement board and use galvanized nails to secure the membrane to the studs.
Install an anti-scald shower valve that can be easily operated. Make sure that it has a hand-held showerhead along with the main head. Tile the walls first and then the floor. Follow the ADA guidelines for mounting grab bars or a shower seat.