Tile and grout are not waterproof. Water gets through them every single day, and what happens next depends entirely on what's underneath. A shower built without a real waterproofing system will fail; the only question is whether it takes two years or ten.
A properly built shower has a continuous waterproof membrane behind the tile on every wall and under the floor, lapped so water always runs down and out to the drain, never into a seam. The floor is sloped toward the drain before the membrane goes in, so water never pools in a corner.
Before any tile goes up, the pan should be flood-tested: plugged, filled, and left for at least a day to confirm nothing leaks. It costs a day of schedule, and it's the single best insurance you can buy for a bathroom. If a contractor skips it, ask why.
When you're comparing bids, ask three questions: what waterproofing system is being used, how the floor slope is built, and whether the pan will be flood-tested. Clear answers to all three tell you more about the finished shower than any tile sample will. Every Silva Remodeling Corp shower gets all three, and we're happy to show you the pan before we tile it.