Installing a Leakproof Shower Pan
A thick mortar bed over a vinyl membrane makes a sturdy base for tile, but it pays to test for leaks
In the past ten years, I have installed well over a thousand shower pans. Of all those pans, only two have leaked. One pan belonged to my father-in-law, and the other belonged to my dentist. My father-in-law is a conservative man who likes to have all his ducks in a row. My dentist was well aware that I had two root canals coming up in the near future. Needless to say, I made sure that fixing these two jobs was at the top of my list.
After a lot of work, I found that faulty drain-assembly fittings were responsible for the leaks in both cases (honest). In the process of rebuilding the pans, I discovered a simple test that would have saved me all that misery. But more on that later; first, let’s start building the pan.
Before I install the pan, I clean the subfloor in the shower area thoroughly. I look for anything that might punch or wear a hole in the membrane in the future. I set any nail heads in the lower 6 in. to 8 in. of the framing, and I put an extra flap of membrane over any nail plate installed to protect the plumbing.
When I’m building a shower pan, my first concern is that the subfloor is structurally sound. If it’s not, I add a layer of 1/2-in. plywood before the plumber sets the drain assembly. I also do an extra step that I think makes a huge improvement over a standard installation. I like to pitch the shower floor to the drain area before I put the membrane material down. A pitched mud base allows any water that may reach the membrane to drain through the weep holes in the drain assembly.