How to Install a Shower Threshold

Measure the opening where the threshold will be placed. If possible, locate the threshold so it is in line with wall studs and floor joists.

Transfer the measurement to 2-by-4s.

Cut three lengths of 2-by-4s to the measured size.

Stack the 2-by-4s in the threshold opening, and attach them to the floor joists and wall studs using 16d galvanized nails.

Continue constructing the shower pre-pan. Place felt paper, the bottom drain piece, metal lath and a mortar layer that establishes the slope inside the threshold. let the mortar cure adequately before proceeding with curb construction.

Cover the shower pan and curb with a waterproof membrane. Measure the shower pan and curb area, and transfer these measurements to the membrane. Size the membrane so that it will extend 8 inches up each wall, and up and over the 2-by-4 curb. Cut the membrane at the wall studs where it must go over the curb.

Attach the membrane to the underlying material using an adhesive suitable for use with the specific membrane material. Glue the membrane down, working from the drain outwards. Staple the membrane for additional security. Place staples only above the level of the curb, and on the top and outer side of the curb.

Glue dam corners into the interior corners of the curb to provide additional reinforcement.

Complete the body of the shower pan. Place the mortar bed with any reinforcement necessary, and tile or otherwise finish the pan surface.

Measure and cut metal lath to fit over the curb, and staple it to the curb only on the top and outer side of the curb.

Set a 1-by-4 or other thin board on top of the curb to serve as a guide for mortaring the sides.

Pack mortar into the metal lath on the curb using a trowel. Check for low or high spots using a level and make any necessary adjustments. Run a float over the mortar to make a smooth surface.

Finish the threshold as desired. To tile it, adhere tiles cut to size to the inside and outside surfaces, fill in the space created at the top with mortar and place bullnose cap tiles on top of the curb.