How to Make a Shower Threshold

Remove any materials necessary to expose the subfloor.

Measure the opening at the threshold where the curb will be and transfer this measurement to two-by-fours.

Cut three lengths of two-by-fours and stack them at the shower threshold.

Attach the stack of two-by-fours to form the curb at the threshold using 16d galvanized nails.

Construct the shower prepan up to the point where waterproofing membrane must be placed. This is generally the portion of the shower floor that establishes the slope by building up mortar to different thicknesses. The mortar is placed atop building paper and metal lath and usually must be allowed to cure for at least a day before the membrane can be placed.

Measure the shower pan area and, taking the walls and curb into consideration, transfer measurements onto a waterproof membrane. The membrane should extend at least 8 inches up each wall and up and over the curb.

Cut the membrane to fit and place it on the shower floor, cutting small slits for the drain bolts and an opening at the drain. To fit the membrane snugly over the curb, cut the membrane for the curb at the wall studs.

Attach the waterproof membrane to the shower pan and curb. Working from the drain toward the wall, apply an adhesive suitable for the specific membrane material and press the membrane to the underlying mortar and wood. Fold the excess material in the wall corners over to form a flap and glue this flap to the wall. Staple the membrane to the walls and curb for added security, but only place staples above the level of the curb. Only staple the top and outside of the curb.

Glue a dam corner into each interior corner at the threshold.

Complete the mortar bed and tiling for the shower floor.

Measure and cut metal lath to fit over the curb.

Staple the metal lath to the curb. Only place staples on the top and outside of the curb.

Mortar the curb. Hold a flat, thin board on the top of the curb and press mortar into the metal lath on both sides using a trowel. Use the flat board as a guide to help make the curb mortar uniformly thick. Check for evenness with a level and make adjustments as needed. Use a wooden float to smooth the mortar surface.

Finish the curb as desired. Typically, the curb will be tiled to match the tiled shower floor. In this case, use a tile cutters to cut tiles so that the top of the tiles for the outside is slightly higher than the top of the tiles for the interior of the curb. Use a thin layer of mortar to attach the tiles and check with the level to make sure they are even. Fill in the top of the curb with mortar and place a bullnose cap tile on the top of the curb to overhang the tiles slightly.