When I started tiling, we didn’t do our own shower pans—that job fell to the plumbers. They put down a lead or copper liner in the framed shower, and then we put in the sloped mud base. When vinyl membranes came along, the plumbers could whip through the process quickly—too quickly, actually. As we put in the mud layer, we often felt chunks of debris under the membrane that would almost certainly wear through and cause leaks.
On one job, the shower developed a leak, and when I tore out the tile, I found that a roofing nail had been left under the membrane. The thin edge of the nail head had sliced through the membrane under the weight of the mud layer. Not wanting to get into a finger-pointing session with the plumber, I fixed the problem and ate the expenses. At that point, I decided to do my own shower pans—start to finish.
Taking over the whole process made sense. Leaks became all but nonexistent, which meant happy clients and fewer callbacks. But it also let us control every step of creating a tiled shower. A leakproof shower starts with the shower pan, but there are other critical steps, as well—most of which happen before any tile is installed.
A strong floor under a shower pan is crucial, but less so than under a tiled floor. The 2 inches or so of mud base adds even more rigidity to the floor of a shower. In new construction, the floors almost always meet the Tile Council (TCNA) guidelines for deflection; in remodels, I reinforce the floor framing from underneath the shower if I have any doubts.
I also make sure the wall framing is finished with adequate nailing for the membrane and the backerboard. The TCNA suggests blocking around the bottom perimeter of the shower to back up the membrane as the mud layer goes in and to support the bottom edge of the backerboard. But when I use 1/2-inch Durock as backerboard, I find that this blocking isn’t necessary on my installations.
Lastly, I make sure that the shower drain is permanently installed, and that all the parts are there. The last thing I need to find out when I start to install the pan and mud layer is that the plumber has to remove the drain for some reason, or that I’m missing a part.