How to Build Shower Pans

These days, if you want to put in a shower, you can just go to a home center and pick up a fiberglass unit. Before that was possible, pros had to build a custom shower pan by mixing and applying mortar, troweling it flat, and laying ceramic shower floor tile.

Although fiberglass units make shower pans quick and easy, they lack the elegance of a handcrafted mortar and tile floor. So if you’d like to install a tile shower and are willing to build your own custom shower pan, you’ll be able to tile it to match the walls. And with a mortar and tile floor, your shower can be any shape. (For instance, see How to Install a Glass Block Shower.) In fact, no matter what its shape, if the shower you have in mind doesn’t conform to the rigid size requirements of a manufactured base, a mortar floor may be your only alternative.

You’ll find that the cost of the materials used in a hand-crafted base is roughly the same as the cost of a comparably sized fiberglass pan. The downside is that instead of just plugging a manufactured unit into the opening, you’ll have to do a lot more work. You’ll need a couple of days to form and tamp in two layers of mortar, deal with some tricky vinyl membrane liner and then install the tile. Installing shower pans isn’t a project for winging it or taking shortcuts. Poorly installed shower pans will leak, and the only correct way to fix a poor installation is to rip out not only the base but also the shower walls.

The shower pan installed in this project is somewhat complicated, but the fundamental techniques are the same for even the simplest shower — one the size of a phone booth. If you have experience with cement and some basic trowel skills, you should be able to do almost any size shower floor in less than two days, excluding tile work.

Anatomy of a Mortar Shower Floor

The first layer, called a sloped fill, is simply a mortar subfloor. It’s sloped toward a special two-piece clamping-type drain (available at any home center) that is made specifically for a mortar bed shower floor. The sloped fill slants from the drain toward the perimeter of the shower with a slope of ¼ inch per foot. Since our shower had an average width of 3 feet, we sloped up from the ¼-inch thickness of the drain to a 1-inch thickness around the shower walls and curb to get the necessary ¾-inch slope.

The second layer, called the pan, is a durable CPE (chlorinated polyethylene) membrane. This vinyl liner is turned up at the edges to create a waterproof membrane in the shape of a shallow pan. Water that works its way through the grout and the top layer of mortar will flow down the slope to be drained through the weep holes of the drain. On top of the pan is a layer of expanded galvanized metal lath to reinforce the mortar. Over the lath, a sloped mortar bed is laid using the same ¼-inch-to-the-foot slope rule we used for the sloped fill.

Shower curbs help by containing water in areas that aren’t bordered by walls. If a drain becomes blocked, perhaps by a washcloth over the surface, a curb buys you time. It will dam the water within the shower for a while before it lets it run over onto the bathroom floor.

(For a larger version of this drawing, see Additional Information, below.)

Draw the Floor

• Draw the outline of the shower floor on the subfloor to use as a pattern for setting the mortar forms.
• Nail an 8d nail next to the wall and strike a 65-inch arc for the curved form board.

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