“A crunching sound is coming out from recently installed ceramic tile in my bathroom! The grout is coming up and the tiles seem to move slightly as I walk on them. What is causing this?”
Tile Installation and Grout Repair It sounds like your tile was installed on a subfloor that was not completely level and secure. When laying tile , we typically recommend using cement board, such as Tilebacker or WonderBoard, as a base. If plywood is used, a minimum ¾” plywood reinforcement on top of the subfloor is necessary for a sound base. This is especially important with large tiles, which are more likely to crack without a sturdy foundation.
In your bathroom , it seems likely that either thin plywood was used, or that the cement board wasn’t screwed down securely. Unfortunately, there is no quick fix. Regrouting will not solve the problem. If your tiles are moving and grout is disintegrating, the only real solution is to rip up the existing tile and install new tile.