How to Install Rubber Membranes for Ceramic Tile
- 1). Find the distance from all four walls of the shower to the drain. The plumber should have roughed in the drain. Use a clamping ring drain with two pieces. The bottom of the drain is a backup for any water seepage and the top is just the normal drain. Use the measurements to calculate the slope. You'll need a drop of 1/4 inch for every foot to the wall from the center of the drain. A wall that's 3 feet away needs the concrete 3/4 inches high at the wall and slope down to less than 1/4 inch at the edge. Make a pencil mark on the wall studs for the concrete height.
- 2). Mark several points with the height of the outside concrete. Use a level and a straight edge to draw a line all the way across the wall. Check it with the level. Set the clamp ring for the drain in place but don't clamp it down. You'll need to cover it to prevent debris from going in the drain.
- 3). Lay 15 lb roofing felt on the floor. This provides protection for the concrete from drying too quickly and curing improperly. Overlap the felt where the edges meet. Put a layer of galvanized wire mesh on top of that and nail it down to the sub floor. Mix 1 part Portland cement with 3 to 4 parts sand. Put just enough water to allow it to roll in a ball but not crumble easily. Some contractors like to add latex additive in place of the water.
- 4). Build the layer of concrete all the way around the walls up to the line you marked. Many contractors like to put a thin layer around the drain and then fill in between the two. Whatever way you choose, make sure the surface is sloped properly, packed and leveled smooth with a board. Let this layer of cement dry overnight before you continue to the next step.
- 5). Coat the top of the concrete with a layer of thinset. Lay out the rubber membrane on the floor while it dries. Transfer all the measurements from the shower to the membrane with a felt tip marker. Make sure you allow for the membrane to go up the wall at least 2 inches higher than the threshold and allow for the membrane to cover the threshold. Before you install the membrane, put waterproof tape at the corner gussets and on the joints. Install the membrane. Remove the drain cap. Secure the membrane to the drain with plastic cement 1/2 inch from the drain. Put the drain cap in place again and lock it down to seal the membrane. Staple the top of the membrane at the top around the walls. Fold the corners like a hospital bed sheet. Seal all the seams, particularly at the threshold where you'll cut an extra piece to lie over any exposed seam. Allow the area to dry thoroughly then plug the drain and fill it with water to set overnight to test if it's watertight.
- 6). Attach concrete backerboard to the outside of the curb and after you wrap it in wire mesh. Insert the barrel back into the drain. Make sure you have it adjusted for the final height. Put pea gravel on the weep holes, the holes on the outside of the drain that allow any water that got under the top concrete to drain, so the new layer of concrete doesn't clog them. Put down an inch of concrete then put a layer of wire mesh. Add the final layer of concrete. Don't forget to fill in the threshold and pack it tightly.
- 7). Use a board to screed the floor and make it smooth. Allow the floor to dry then put the concrete backer board on the walls. The rubber membrane for the ceramic tile is complete. All you need to at this point is a layer of thinset as the adhesive and the tile. Don't put down more than what you can finish in a 20 minute period.
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