A shower is waterproofed with a sloped shower pan and a waterproofing membrane behind the tile, not with tile and grout alone. Tile and grout shed most water, but some always works through. The membrane stops it before it reaches the framing or subfloor, and we water-test the pan before any tile goes in.
Grout and most tile are not waterproof on their own. Water slowly works through grout lines, and in a shower without a proper barrier it reaches the wood framing and subfloor, where it leads to rot, mold and failed tile over time. Many leaks found during bathroom demolition trace back to an older shower built without a continuous membrane, or with one that was damaged. That is why the waterproofing layer matters more than the tile you see, even though no one notices it once the shower is finished.
After demolition, we install backer board on the shower walls and build a shower pan sloped toward the existing drain so water does not sit on the floor. A waterproofing membrane goes over the pan and up the walls, with seams, corners and the valve and drain openings sealed so the barrier is continuous. Niches and benches get the same treatment as the walls, since a ledge that holds water is a common weak spot. The membrane ties into the drain so any water that gets behind the tile is carried down and out.
Before tile goes in, we water-test the pan. We plug the drain, fill the pan with water and leave it to sit, then check that the level holds and no water escapes. If a problem turns up, it is fixed while the pan is still exposed, which is far easier than tearing out new tile later. Once the pan passes, we set tile and grout. Waterproofing is part of every shower we build, including tub-to-shower conversions, and it is included in your written estimate rather than offered as an upgrade.
Answered by Legacy Construction & Design · CA License #790442 · October 2026