The most common failure in custom tiled showers is omitting the pre-slope.
You must pitch the subfloor underneath the waterproof liner, not just the mortar bed on top of it. Without a pre-slope, water that permeates the grout collects on the flat liner, becomes stagnant, and creates a "mud sandwich" that leads to mold and liner rot. 2. Blocking for the Future
Behind the location of heavy floating stone benches or large glass door hinges.