How to Build a Shower Pan Bumper

Construct the base for the bumper while the subfloor is exposed and before the mortar for the pre-pan is placed. Begin by measuring and cutting three 2-by-4-inch pieces of lumber to fit the space. Stack them, and attach them to floor joists and wall studs at the shower threshold using 16d galvanized nails.

Build the shower pre-pan. This task generally involves attaching building paper and metal lath to the subfloor and gluing the bottom drain piece of a three-piece shower drain into the drain opening before laying mortar in a manner that establishes the slope of the shower floor. Let the mortar cure for at least one day before continuing.

Measure and cut waterproof membrane to fit the shower pan and bumper. Cut the membrane so that it will extend at least 8 inches up each shower wall and up and over the bumper. Cut small slits for the drain bolts and opening, and attach the middle drain piece of the three-piece shower drain, tightening the bolts to create a watertight seal.

Attach the waterproof membrane to the underlying mortar and wood. Use an adhesive suitable for the specific type of waterproof membrane. The membrane can be stapled to the walls and bumper for added security, but staples can be placed only around the top edge of the membrane on the walls and on the top and outside of the bumper.

Glue one dam corner into each upper corner on the interior of the bumper for added reinforcement.

Cut metal lath to fit the bumper, and attach it to the bumper. Bend it tightly to fit, and staple it to the underlying wood on the top and outside of the bumper.

Apply mortar to the sides of the bumper. Pack mortar into the lath with a trowel, and place a thin board, 1 by 4 inches or 1 by 6 inches, on the top of the bumper to use as a guide. Smooth excess mortar, check for evenness with a level and make corrections as needed. Let the mortar cure for at least one day before proceeding.

Prepare tiles for the bumper if tiling is the desired finish type. Place the bumper tiles after the mortar bed and tiling for the floor of the pan are complete. The tiles on the interior side of the bumper should extend 1/2 inch above the unfinished bumper top, while tiles on the exterior side should be cut so that they extend 5/8 inch above the bumper top. This space creates a slight slope that will force water toward the drain. Use tile cutters to cut the tiles, or score them with an appropriate scoring tool and snap them by hand.

Place mortar lightly on the sides of the bumper, and place the tiles in the mortar. Use a level to check for levelness regularly, and adjust the tiles as needed.

Pack mortar into the space created at the top of the bumper. Remove excess mortar, and fill low spots to make this mortar flush with the top of the side tiles. Let the mortar cure.

Lay a thin layer of mortar, and place bull-nose cap tiles on the top of the bumper. Put all the bull-nose cap and other tiles in place.

Grout, clean and seal the tiles on the bumper and throughout the rest of the shower.

Caulk all joints and corners with a bead of silicone caulk.