- 1). Take measurements of the area that you have framed for the shower. Once you rough in the drain, you'll need to measure the distance from the center of the drain to all the surrounding walls. These numbers are to find the appropriate slope for the shower stall floor. If you want a leak proof shower, you need to make sure that the water drains adequately. The slope needs to be 1/4" per foot of distance. If your wall is 3' from the center of the drain, the concrete line on the outside is 3/4" up and angles down to 0 in the center of the drain.
- 2). Mark the height on the boards for the height of the concrete. Make several marks and then join them together to make a line. Check the line with a level. Before you begin to pour the concrete, you'll place the drain's clamp ring in place, but don't clamp it yet. Use masking tape to cover the opening in it and protect the drain from concrete entering it.
- 3). Roll a layer of 15 lb felt onto the floor. You can use plastic also. Make sure that the edges overlap. This prevents the sub floor from drying the concrete pan too quickly and compromising its strength. Put galvanized mesh wire over the layer of felt and either nail it down with roofing nails or use galvanized screws. In a large container, mix 3-4 parts of sand for each part of Portland cement. Add just enough water to make it firm but not crumbly. Some people recommend a latex additive instead of water. Others feel this is a waste of money and time.
- 4). Lay the concrete around the perimeter to the height you marked. Work the concrete around the drain with a thin edge then connect the two together by filling in the area in between. Use a level to make sure you have a slope. The slope is one key to a successful shower that doesn't leak. You can use a board to pack, tamp, it down and then smooth, screed, the top with the board. Allow the concrete to dry at least overnight before you begin the next step.
- 5). Top off the concrete with thinset. While you wait for the thinset to dry, lay out the rubber membrane and mark all the measurements on it. You need the membrane to go up the wall at least 2" beyond the height of the curbing or threshold. You also need to cover the threshold with the membrane. Waterproof the corner gussets and all the joints and connecting areas with waterproof tape. Lay the membrane. At the drain, you need to take off the drain cap, connect the membrane securely with plastic cement about 1/2" from the drain, and then replace the drain cap. Lock the cap down, and it will seal the membrane. Use staples at the very top of the membrane to connect it to the walls. At the corners, fold them like hospital corners on a bed sheet. The biggest key is to seal all seams thoroughly, particularly at the threshold. You'll need to use extra pieces to cover all exposed seams and corners. Once you've sealed it, let it dry thoroughly, at least overnight, and then perform a water test on it. Fill the area with water, let it stand for ten hours and see if you have a leak.
- 6). Remove the water and let the area dry. Wrap the threshold with mesh wire and then put up backerboard on the outside of the threshold. Put the barrel of the drain back into it and adjust it to the final height. Protect the weep holes of the drain, the openings on the outside of the drain, with pea gravel. Lay an inch of concrete, a layer of wire mesh and finally, the last of the concrete. You'll need to pack the mesh on the threshold tightly with concrete.
- 7). Level the area with a board. Once you have screeded the floor smooth, allow the concrete to dry. Put up the backerboard on the walls. While concrete backerboard is good, it's difficult to use. There are newer types of board that resist mold but are easier to cut and hang. Don't nail below the line where you put the rubber membrane. You just need to finish the shower in any way you wish, because the shower pan is now leak proof.
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