Building Shower Pan Fundamentals

Traditional tile shower construction involves the use of mortar to build a base for the laying of the tile floor. The building shower pan fundamentals include just a few basics but what makes it more complicated are all the variables that get introduced because of all the different situations that exist. Installations can be over all sorts of materials for example. Here are a few basics that even so-called pros get wrong.

No matter what, the tile floor must be built over a rigid floor. Now that does not mean only showers work well and last if built over a concrete floor. That's not so at all. But if built over a wood sub-floor, the floor must be properly braced so that movement of the floor is at a minimum. In fact the specs for shower installation specify how much sub-floor movement or deflection is permitted with a certain applied load. Keeping deflection to a minimum with wood sub-floors is quite simple if the floor is topped with the proper plywood and the floor is braced not far from the shower. With a solid base the tile floor is not at all likely to crack in the mortar joints and fail in that way. Here's another thing.

I have two shower videos showing how to build a shower pan for tile by seemingly professional tile setters. In both cases the tile setters only use one layer of mud sloped to the drain as a base. They both put the shower pan membrane down first right over the sub-floor and then lay in deck mud at a slope to the drain. No doubt this can result in a shower that does not leak for awhile. What it also produces is a shower base that remains soaked with water at all times as long as the shower is use regularly. That's so because the shower floor permits water to seep below the surface all the way to the vinyl liner membrane where it is routed to the drain. Using one layer of mortar in a shower base is a short-cut and poor construction practice. The proper method is well known and takes two layers of mud with cure times between layers. There's more.

Walls of showers are not really part of the base of course. But the intersection of the actual base and the wall often is a failure point. Getting the liner membrane and the wall boards put together properly is quite simple but often this is another short-cut spot too. Running the base up the wall in common ways creates a wick that can easily pull moisture from the mortar base up into the wall and behind the tiles. That's a place for all sorts of toxic messes to get a start...

Any building shower pan instructions must cover all the little places that can lead to shower failure and can lead to leaks down the road...