How to Build a Shower Floor

A tiled shower stall floor has a very specific structure that's designed to provide multiple moisture barriers and diversion, in case water gets under the tiles. The stall is floored with cement board, topped with a layer of sloped cement, then a thick plastic floor liner, then another layer of cement. The liner between the cement layers diverts any escaped water into the drain, through hidden holes in the side of the drain assembly. Building a shower floor is a complicated undertaking that you shouldn't attempt if you don't have some carpentry experience.

  • Tape measure
  • Shower drain kit (with "weep holes'' in the sides)
  • Screwgun
  • Jigsaw
  • 1/2-inch cement board
  • Carpenter's glue
  • 1 1/4-inch galvanized screws
  • Wire mesh for cement
  • Tin snips
  • Staple gun
  • Cement
  • Wheelbarrow
  • Shovel
  • Trowel
  • Shower floor liner
  • Shower liner glue
  • Razor knife
Measure to find the center of the plywood floor of the shower stall frame. Mark the circle for the drain, using the drain assembly. Cut out the circle using your jigsaw.

Cut 1/2-inch cement board with your jigsaw to fit across the whole floor. Cut out the drain hole in the cement board with your jigsaw. Secure the board in place with carpenter's glue and galvanized 1 1/4-inch screws sunk about every 6 inches.

Set the drain assembly into the hole, resting the adjustable top flange over the surface of the cement board. Use your tin snips to cut wire mesh to the size of the floor, snipping out the hole in the middle to accommodate the drain. Staple down the mesh.

Mix your cement in a wheelbarrow according to the packaging instructions. Use a shovel to pile the cement onto the floor, right over the mesh. Make it about 1/2 inch deep around the perimeter of the drain, then use your trowel to slope it up toward the walls at an angle of 1/4 inch for each foot of length. If there's 2 feet from the drain to each wall, the 1/2-inch-thick cement at the drain should be 1 inch thick by the time it gets to the wall.

Let the cement set overnight. Lay the shower floor liner over the cement, draping the overhang up the side walls and stapling it there, and cutting out the drain circle with a razor knife. Glue down the edge of the liner around the drain with liner glue.

Mix another batch of cement and lay it over the liner. Make the second layer 1 inch thick throughout, so the original slope you made is still intact. Set the drain flange into the cement.

Let the second layer of cement cure for a day. Tile the floor.

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