The shower floor is a logical starting point when you're planning to install a steam shower. Very warm and relaxing, a home steam shower is akin to a sauna. When properly installed, it is a great way to unwind after a long day. However, if installed improperly, leaking water vapor will turn to water and wreak havoc on drywall, wood, paint or anything else in its path. Thus, a steam shower must be completely sealed or else you'll have a mold and mildew problem on your hands. There are a couple of ways to go with the steam shower floor. A pre-formed, fiberglass or vinyl shower pan is one option. Another is cement poured over a vapor barrier membrane. This how-to focuses on the shower pan, for it's lighter and easier to work with.
Step 1: Level Subfloor
The pan or base of the steam shower must be installed on a perfectly level subfloor. Determine where you are going to install the steam shower. This is in relation to the location of the shower drain plumbing. Using the level, check the horizontal level of the floor. If need be, mix up some leveling compound and apply a coat of it atop the subfloor. The goal here is to raise uneven spots on the floor to make a level surface. Check your progress with the level tool, and allow to dry once complete.
Step 2: Layout the Shower Pan for Installation
Align the shower pan over the shower drain to layout the installation. In addition to being adhered to the subfloor with strong silicone adhesive, the pan should be fastened to the wall studs. Shower pans feature a flange which has prefabricated holes for setting screws. Match these fastening points with studs or blocking between studs and mark where you will set screws. While doing this, make sure the drain hole in the pan remains aligned with the drain plumbing. Make guide marks on the subfloor on either side of the shower pan indicating exactly where it will go when you affix it.
Step 3: Affix Shower Pan
On the bottom of the shower pan, apply heavy-duty silicone adhesive over the raised webbing using the caulking gun. Run a solid bead of adhesive around the edge of the drain on the floor. Set the shower pan evenly upon the subfloor, using the floor markings as your guide. Apply enough force so the fiberglass pan affixes to the subfloor thoroughly. Make sure the flange holes line up with the marks on the studs. Also make sure the drain holes align evenly. Set the shower pan screws through the designated holes into the wall studs or blocking. Allow the adhesive a day to cure.
Step 4: Install the Drain
Install the drain assembly through the hole in the fiberglass into the fixed plumbing. Follow the installation directions carefully to ensure the washers form a proper seal. Now that the floor is in place, you can install the 1-piece vapor barrier membrane, draping from the ceiling down over the inside of the shower pan splash guard and continue with the walls, ceiling and door.