Installing a Mortared Shower Pan

Custom Showers

If you’re in need of a custom fit shower enclosure, then a mortared shower pan is in your future. For many do-it-yourselfers this project sounds intimidating, but with some basic information and the right tools, an experienced DIYer can handle it.  You’ll need to have some level of comfort with framing, mixing and floating mortar, setting tile, and grouting. If this sounds like way more than you’re bargaining for give All Star Plumbing and Restoration a call, we’ve got years of experience handling these types of jobs.

Step 1: Assuming you’ve already got good plywood subflooring, cut pressure treated bottom plates and pre-assemble the walls. Toenail in some 2×10 blocks between the studs to support the sides of your new membrane. Use 2×4’s to create curbs for sides that don’t brace the walls. Add ¾” guides around the entire perimeter. Finally cut a hole in the center of the floor for your drain plate.

Step 2 : Coat the bottom of the drain with silicone both outside and inside the bolt circle. Now coat the interior of the drain with PVC primer and cement. Connect the drain with the waste line and let everything dry. Insert the drain bolts into the lower drain plate leaving just under 1” exposed.

Step 3: Cut a section of 15 lb. felt to fit the area of the shower bottom and staple it to the floor. Repeat this process with a piece of metal lath. Set the metal in place and cut out a circle over the drain but slightly larger than it. Ensure the metal is lying flat and then staple in place.

Step 4: Mix up some bagged sand mix in a wheelbarrow and dump the mortar onto the shower floor. Use a wood float to slope the floor towards the drain. When you’ve got your slope right, compress the mortar until the surface is even and let it dry for 10-12 hours.

Step 5: Measure and cut the membrane the correct size. Your membrane should be roughly 10” longer than your floor with an additional 6” of length on the front. You’ll want to add a second layer of membrane to the drain area. To do this cut a 9” circle of membrane and solvent-weld it over the drain area.

Step 6: Place your membrane on the floor of your shower. Pull it all of the way forward until it covers the curb. Start at the drain and work your way outward smoothing out any bubbles. Staple the edge of the membrane to your wood blocking.

Step 7: You’ll need to cut the membrane to expose the bolts. In order to do this, feel around until you locate each bolt and use a utility knife to cut a ½” “X” over the bolt. Push the membrane down over the head of the bolt. Unscrew the bolts and fasten the upper drain plate. Place the drain plate over the holes in the membrane and reinsert the bolts. Turn to lock. Use a long knife to cut away the membrane from the drain hole.

Step 8: Fold the extra material in the corners into triangles and solvent weld these in place. Now cover the drain, fill the pan with water, and check for any leaks. You should mark the height of the water and let it sit for at least 24 hours to confirm it’s not slowly leaking out.

Step 9: Wrap the threads of the strainer several times with plumber’s tape. Screw the strainer into the flange. Clean off any grit with a wet cloth. Next cut backerboard to fit the walls and set them on ½” shims. Fasten them to the studs and remove the shims. Caulk the space at the bottom with silicone. Lastly tape and mud the seams with thin set.

Step 10: Spread a final layer of mortar with a slope of about 1/3 of a bubble on a level. Lay metal lath over the first course, then pack and level a top layer. Work in small sections always sloping towards the drain. Bend the lath to fit the curb and pack it as well. Make sure not to clog your weep holes throughout this process.

Step 11: Use a 2’ level and transfer the plane of the bottom of the strainer to the walls and curb. Use a Sharpie to mark the plane on the backer board. You need to be sure you’ve got a slope of ¼” for every linear foot. If you’re slope is correct you are now ready to begin laying tile for the floor.

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