How to Install a Shower Membrane

Installing a shower membrane ensures that your shower floor and enclosure will remain as water-tight as possible. A shower membrane is similar to a swimming pool liner. It is a special type of plastic sheeting that goes around the bottom of the enclosure and the shower pan to prevent water from seeping through gaps and crevices in the shower and into the underlying materials. The lack of a shower membrane can result in rotting wallboard, mold, mildew, and rotten wood studs. In other words, big problems. It is a simple and inexpensive piece of material that will make all the difference in the life and performance of your shower. Here you will find some tips on installing a membrane in your shower enclosure. These instructions are based on the assumption that the concrete base has already been poured.

Measure the Membrane

First, measure the size of the shower pan, from all dimensions. You will want to install the membrane after the initial layer of concrete has set up, but you don't have to wait until it is totally cured. Generally, letting it cure overnight before installing the membrane is fine. Lay the membrane out on the floor, and transfer your measurements onto the membrane. You will want the membrane to extend between 9 and 12 inches up the side walls for the full amount of protection, so plan your measurements accordingly. Mark out the measurements with a permanent marker and use a utility knife or good scissors to cut it. Don't forget to cut out a space to accommodate the drain.

Fit the Membrane

Lay the membrane in the shower pan, and adjust it as needed. You will want to install the membrane before the backer-board usually. The membrane will bunch up in the corners. It is important to wedge the membrane back into the space between studs and get it as smooth as possible. If there is a hump where a wad of membrane is you will see this once the tile or surround is installed, so take some time to make sure it is done well. If you hang your backer-board first, leave quarter-inch gaps in the corners to bunch the material into.

Secure the Membrane

Use rubber cement around the opening in the liner next to the drain. Cement approximately one half inch to one inch of the material to the shower pan around the drain. Finally, use the waterproof tape in the corners and around the edge of the membrane to seal it.

Finish the Shower Pan

Finally, pour the final layer of concrete over the membrane, to equal the height of the drain. Smooth and scree the final layer to a smooth finish, and let cure. You will want to have the drain height pretty much set at this point, as you will not want to have to adjust the height once the final layer of concrete is poured. Once the shower floor is complete, you are ready to finish the shower.