The tile is the part you see. The membrane behind it is the part that decides whether this was money well spent.
A shower is best understood as a waterproofing system that happens to be finished in tile, not a tile installation that happens to get wet. Everything about how it's built follows from that.
Grout is a porous cementitious or epoxy fill between tiles, and water moves through it in ordinary use — that is not a manufacturing defect, it is how grout has always worked. If grout were the only thing standing between shower spray and your framing, every shower would fail within a year.
Moisture-resistant drywall, commonly called green board, resists incidental dampness better than standard drywall. It is not rated as a waterproofing membrane for a wet-area assembly, and treating it as one — instead of building a dedicated waterproofing layer over or in place of it — is one of the most common reasons showers fail well before they should.
A proper shower assembly has a continuous waterproofing layer built across the walls, the curb, the niche and the pan, installed and detailed so water that gets past the tile and grout is directed to the drain rather than into the wall cavity. This layer is what actually keeps the structure dry. Once tile goes over it, you will never see it again for the life of the bathroom.
The flat walls are the easy part. Where the shower pan slopes to the drain, where the curb transitions from dry to wet, and where a niche interrupts the wall are the places waterproofing details are hardest to get right and most likely to be shortcut.
Every plane change needs a flexible joint, not rigid grout, because the building moves slightly and grout cannot move with it. A caulked corner that has been quietly replaced with grout at some point is a common, avoidable failure point.
Once the tile is set, the waterproofing is gone from view for good. That is exactly why it is worth asking directly, before work starts, what waterproofing system is going behind your walls — not just what tile is going on top of them.
Describe the job and we'll match you with an installer who builds the assembly in the right order.
Get a Tile InstallerA rough description is plenty — we will follow up to scope the details and set a time.