How to Make a Shower Bed

Remove any materials in and around the site necessary to expose the subfloor.

Construct the frame for the shower pan. Measure the opening at the shower threshold where you will place the curb and transfer this measurement to 2-by-4-inch wood. Cut three lengths of 2-by-4s to this size, stack them at the threshold and attach them to the floor joist and wall studs using nails. Measure the bays between wall studs around the shower perimeter, cut 2-by-10s to this size and install them at the bottom of the stud bays to create a low wall around the shower.

Cut a section of building, tar or felt paper to fit the bottom of the shower and secure it to the subfloor using staples.

Glue the bottom piece of a three-piece shower drain into the drain opening using PVC cement. Stuff a piece of cloth in the opening to prevent loose mortar from accidentally falling into the drain.

Plan for the establishment of the slope in the pre-pan layer. Measure the distance between the center of the drain and the wall farthest from the drain. The floor height should increase at least 1/4-inch per foot between the drain and the wall. Calculate the total rise required. Use a level to mark the height of the bottom drain piece on the wall. From this spot, measure up the distance of the total required rise and use a level to draw a line around the entire perimeter at this height.

Staple a section of metal lath or wire mesh to the subfloor. Cut it to fit within the shower pan and leave a 1/2-inch gap around the shower drain.

Prepare the mortar for the pre-pan. Mix the mortar so that it has a fairly dry consistency. Use an additive to increase strength, if desired.

Pack the mortar into the metal lath and build it up between the drain and the line drawn on the wall using a trowel. Once the slope is roughly established, hold a level or straightedge with one end on the drain and the other end at the line on the wall and run it around the perimeter of the shower to recognize and correct any low or high spots in the mortar. Run a float over the mortar to smooth the surface. Let the mortar cure for about a day before continuing.

Measure and cut waterproof membrane to fit the shower. Size the membrane so that it extends 8 inches up each wall and up and over the curb. At the curb, cut the membrane at the wall studs so it easily fits over the curb. Cut small slits for each of the drain bolts and an opening for the drain.

Adhere the membrane to the underlying material using an adhesive suitable for use with the specific type of membrane material. Work from the drain outwards. For extra security, staple the membrane to the wood but only place staples above the level of the stacked wood curb and on the top and outside of the curb.

Glue dam corners into the curb's interior corners.

Install the middle and top drain pieces. Remove the rag from inside the drain. Use drain bolts to fasten the middle drain piece to the bottom drain piece and tighten the bolts to create a watertight seal. Attach the top drain piece and adjust its height to reflect the depth of the planned mortar bed plus the tiles or other surfacing. Place spacers in the drain holes to keep mortar from filling them.

Mark, on the wall, the planned height of the mortar bed. Use a level to draw a line around the shower perimeter at this height.

Prepare the mortar and build up the bed to about half of its planned depth.

Cut a piece of metal lath to fit, again leaving a small gap around the drain, and press it into the mortar.

Build up the remainder of the bed with mortar. Use a straightedge or level to check for evenness, make adjustments as needed and float the surface. Let the mortar cure adequately before placing tiles or other finishing materials.