How to Do a Build-Up Pan for a Shower

Measure the dimensions of the shower floor. Cut a piece of 3/4-inch plywood to fit.

Measure and mark the location of the drain hole in the shower floor. Cut a corresponding hole into the plywood with a jigsaw.

Place the plywood on the floor, aligning the hole in the plywood with the drain hole.

Stand a 2-by-10-inch board on edge against the bottom of the wall framing on each of the three sides where the shower walls will be. Nail the boards to the wall studs.

Lie three two-by-fours stacked on top of one another on the floor where the shower door is being placed. Nail them to the floor.

Cover the plywood with roofing felt, then staple it to the floor with a hammer stapler. Lie mesh over the roofing felt, then staple it to the floor.

Use a utility knife to cut through the roofing felt and mesh to expose the drain hole.

Slide the bottom flange of the drain assembly into the drain hole. Place duct tape over the bottom flange to prevent mortar from entering.

Mix mortar for the shower floor, following the instructions on the package.

Place the mortar onto the shower floor, using more mortar around the edges of the shower and less near the drain hole.

Smooth the surface of the mortar with a two-by-four. Slope the mortar so it's about 1 1/2 inches lower near the drain hole than it is around the perimeter of the shower floor.