How to Do Curb on a Shower Pan

Build the base for the curb while the subfloor is still exposed, before construction paper is placed. Cut 2x4s to fit and attach them to floor joists and studs at the shower threshold using 16d galvanized nails. A stack of at least 3 2x4s is suitable for this task.

Construct the pre-pan. Attach construction or building paper to the subfloor, glue the bottom drain piece into the drain opening, plan for the slope required in the pre-pan mortar layer, secure metal lath atop the paper and lay mortar for the pre-pan. Pack the mortar into the lath and build it up to the line on the wall, using a level to check for evenness and a trowel and float to make adjustments and smooth the mortar surface.

Measure and cut waterproof membrane to fit the shower. The membrane should be sized so that it will extend 8 inches up each wall and up and over the curb. Once the membrane is placed, cut slits for the drain bolts and a small hole for the opening, then attach the middle drain piece and tighten the bolts to create a watertight seal.

Attach the membrane to the mortar and wood using an adhesive suitable for use with the specific membrane material. Staples can be used to secure the membrane but should only be placed around the top edge of the membrane and on the top and outer side of the curb.

Glue dam corners into each corner where the curb meets the shower wall for added reinforcement.

Measure and cut metal lath to fit tightly over the curb.

Secure the metal lath to the curb. Bend it to fit tightly over the curb but only use staples or nails to attach the metal lath on the top and outer side of the curb.

Mortar the sides of the curb once the shower floor has been completed. Trowel mortar onto the lath and place a thin board on the top of the curb to use as a guide before running the trowel or float over the mortar. Use a level to check for evenness and let the mortar cure overnight before continuing.

Prepare tiles for the curb sides. The tiles that will be placed on the interior side of the curb should extend a half-inch above the top of the unfinished curb and the tiles on the shower exterior should reach 5/8 inch above the curb's top to allow for slope. Use a scoring tool to mark the tiles where they must be broken and simply break them by hand.

Install the tiles on the curb. Attach the tiles with a thin layer of mortar and check the tiles regularly for evenness using a level.

Pack mortar into the space at the top of the curb and scrape off excess mortar to make it flush with the tops of the side tiles. Let the mortar cure.

Install bullnose cap tile on the top of the curb.

Continue shower construction. Once the walls have been placed, the entire area can be grouted, cleaned and sealed.

Apply a bead of silicone caulk to all joints and openings in the shower.