How to Build a Shower Stall Pan

Prepare the site for the shower base. Remove any materials necessary to expose the subfloor. Cut and attach three 2-by-4s to the floor joists and wall studs at the shower threshold, to form the curb. Cut 2-by-10s to fit and install them in the stud bays around the shower perimeter.

Measure and cut building paper to fit the shower base and staple the paper to the subfloor. Cut an opening in the paper to accommodate the drain opening.

Glue the bottom piece of a three-piece shower drain into the drain opening and stuff a rag into the drain to keep mortar from accidentally falling into the drain.

Plan the slope for the pre-pan. This is the layer in which slope is established. The shower floor should have a minimum slope of 1/4 inch per foot. Measure the distance between the center of the drain and the farthest wall, and calculate the total required rise.

Measure and cut metal lath to fit in the bottom of the shower. Cut a hole for the drain, leaving a half-inch space around the drain. Staple or nail the metal lath to the floor.

Apply mortar to create the pre-pan. Pack mortar into the metal lath and build it up to reflect the planned slope. Once the slope is roughly created, place the level or a flat-edged board with one end on the drain and the other at the line on the wall. Run the level around the pan and identify and correct any low or high spots. Smooth the surface with a wooden float. Let the mortar cure for at least a day before continuing.

Cover the mortar pre-pan and wooden curb with waterproof membrane. Measure and cut the membrane so that it extends 8 inches up each wall and up and over the curb. Cut small slits for the drain bolts and a hole for the drain opening. Attach the membrane to the underlying surface with a suitable adhesive.

Attach the middle drain piece to the bottom drain piece. Tighten the bolts to create a watertight seal.

Prepare to create the mortar bed. The bed should be at least 1 1/2-inches thick. Attach the top portion of the drain, the strainer, and adjust the strainer height to reflect the planned mortar depth. Mark the height of the planned bed around the perimeter of the shower.

Place about half of the mortar in the pan, lay down a piece of metal lath to cover this portion of the mortar, and top off the remainder of the bed. Let the mortar cure for at least a day before applying tiling or another finish.

Complete the curb. Cover it with metal lath that is attached only to the outside and top of the curb, to avoid puncturing the membrane on the interior of the curb. Mortar and tile or otherwise finish the curb.

Grout, clean and seal any tiling.

Apply a bead of silicone caulk to any joints in the pan.