How to Build a Bathroom Floor for a Walk-in Shower

Determine where in the shower you want the floor drain to be situated. Design the walk-in shower around a floor drain that sits along the wall, so that the floor drain sits in a back corner of the shower instead of in the shower’s center. This helps keep the water inside the walk-in shower floor.

Measure the area around the floor drain once you determine where you want to situate the drain in the shower. If you still want the floor drain to lie in the shower’s center, measure across the top of the floor drain in one direction, marking the floor on either side of the drain where you want the edge of the walk-in shower to lie. Then, measure in the perpendicular direction, marking the sides. If you want the drain in the corner, measure the lengths for the shower floor edges so that the drain remains in the corner of the floor markings.

Lay masking tape across the floor where you marked the sides for the shower pan to create a square or rectangular shape on the floor’s surface. Remove any walking flooring, such as tile, hardwood or linoleum, from inside of this marked square.

Take up the floor boards of the subfloor beneath the walking floor if the subfloor is made from wood. Cut the floor boards in that area of the floor with a circular saw set to the same depth as the floorboards. Pry the boards up with a hammer to expose the joists in the floor.

Set the circular saw to 3 inches deep. Cut into each end of each joist in the area where you want to install the walk-in shower to this depth. Place the saw blade against the side of the joist against the first cut that you made. Run it down the length of the joist to the other cut in order to cut that entire 3 inch deep strip out of the top of the joist.

Measure the distance between the joists from which you removed the top wood in the area of the shower pan. Cut enough wood boards of this length to have a wood board every 6 inches between the joists in the shower pan area. Use wood boards that sit exactly ¾ inch shorter than the trimmed joists. Bolt the joists to the floor.

Measure the length of the opening between the joists and. Cut ¾-inch plywood in this size. Place it over top of the wood boards that you bolted between the joists. Nail the plywood to the wood boards. Use a jigsaw to cut a hole in the plywood for the drain.

Cover the new wood flooring surface with a vinyl shower liner. Use a utility knife to trim a hole in the liner in the location of the drain. Place waterproof sealer to attach the liner to the floor around the drain and drywall mud to attach the remainder of the liner.

Spread ready-mix mortar over the liner with a trowel. Spread a roughly 1-inch layer of the mortar over the entire lined surface of floor inside the masking tape edges that you created. Then, gradually build the mortar up as you move to the outside of the space, so that only 1 inch of mortar sits around the drain, but the mortar extends up to the surrounding floor at the edges, making the outside edges about 3 inches deep.

Let the mortar dry for the time the manufacturer recommends. Install a sloped fiberglass shower floor, tile or another shower covering over the walk-in shower base.