How to Build a Cement Shower Pan

Once you use the shower, you'll realize that all the work on the cement shower pan was worth it.

If you've taken on the task of remodeling the bathroom or are adding a new half-bath, you probably have plans to install a shower. Building a cement shower pan is time consuming, and any error leaves you with a huge mess when you attempt to correct it. In order to build a cement shower pan, you need to be precise on a few of the steps.

Things You'll Need

• Boards
• Tape measure
• Pencil
• Galvanized nails and screws
• Power drill with screwdriver bits
• Hammer
• Screwdrivers
• Staples and staple gun
• Clamping ring drain
• Mesh
• Utility knife
• Mesh nippers
• Framing square
• Level
• Chalk line
• 15 lb. roofing felt
• Portland cement
• Sand
• Latex additive for concrete
• Trowel
• Mixing tray
• Membrane
• Sealant
• Pebbles or pea gravel
• Wrench
• concrete backer board
• Carbide tipped knife to cut backer board

Instructions

1. Build the shower stall framework. If you are putting in a new shower, you need the framework for the area. Center the drain if possible. The best type of drain to use when you build a cement shower pan is a clamping ring drain. The base part is a backup in case water gets into the membrane underneath the floor. Its second part, the top, acts as the normal shower drain.

2. Measure the distance from all outside edges to the drain. You need a slope so water doesn't stand. In order to create the appropriate slope, you'll raise the outside edge 1/4 inch for each foot from the drain to the side. If the wall is 3 feet from the drain, then the rise at the outside edge is 3/4 inches. Guide strips of wood cut to size, in this case 3/4 inches tall, and attached to the edge, is a great way to guarantee an accurate slope. You can also simple measure the space from the floor up the side of the wall and mark it.

3. Lay down 15-lb. roofing felt and galvanized wire lath on top of it. Tar paper is a great additional protection for the sub floor. Before you staple down the two, place the clamp ring section of the drain on the subfloor, in position. Don't clamp it down yet. Protect the drain by covering the opening. Set the clamp ring drain on the subfloor but don't fasten it. Staple the 15-lb. tar paper and wire lath.

4. Mix the concrete. You'll need to use Portland cement and sand, and for a strong floor, use a latex additive rather than water. The additive gives the concrete more strength. Pour the concrete and cover the guide boards as you slope it down toward the center. You'll need to tamp it down and screed it with a board if necessary. Let this layer of concrete dry overnight.

5. Add another layer of tar paper, roofing felt, on top of the new concrete you poured the previous day. This gives added protection to the membrane because it's a buffer between it and the cement. Calculate the measurements and transfer it to the membrane. Center the membrane in the shower and cut a small area for the drain. Take off the clamping bolts on the drain. Dab a bead of silicone around the flange and press down the membrane. Replace the bottom of the drain and seal the edges with silicone or other sealant. Cut away the excess membrane in the center of the drain.

6. Put the edges of the membrane on the walls and smooth it into place. You need to fold the corners as you would on a hospital bed. Nail down the membrane to the wall studs and over the trim and threshold. Attach the concrete board on the lower part of the wall. Make a mark all the way around for the height of the second layer of concrete. When you build a cement shower pan, always check your measurements with a level.

7. Adjust the drain screen to its finished height. Put small pebbles or pea gravel at the base around the weep holes. This prevents them from clogging shut. You'll need to apply the wire mesh to the threshold at this point. Pour and smooth out half the concrete on the floor and then add a layer of wire mesh for strength. Apply the rest, smooth it and check the slope. When you build the cement shower pan, the slope and waterproofing are the two most important parts of the job.