Tile – How to fix cracked bathroom tiles

Unless you are concerned about an asbestos material under the tile (such as old linoleum squares), I would remove any old material and start clean. If you keep building on top of the old materials, you might need to rip all your doors down to make them fit with the new floor. Conversely, you need to consider how high to make the new floor in relationship to the old floor. Last, while you may still need floor leveler, a better bet is to install a nice new clean level underlayment board such as concrete board, durarock, hardibacker, or other tile board for tile or a nice clean 1/4" sheet of plywood and paper for hardwood.

If the tiles are cracking, it's probably (edit: might not be) not just the plywood. The floor is flexing in some manner. Tiles need a very rock solid underlayment.

So pulling up the tiles and then pulling up the subfloor and then relaying a new subfloor may not actually fix your problem.

The joists may be flexing (and this is probably the issue) which would cause the floor to crack.

How old is the building? If the build is quite old, the joists may be further apart or sized smaller than current code.

There are a few solutions, once you determine the problem:

• sistering the joists

• adding cross joists under the existing joists

• adding lolly columns under the floor

I fixed a floor on the third floor of a 100 year old house by pulling up the plywood and gluing and screwing half inch subfloor. The floor was rock solid, but we still didn't put back ceramic tile - we went for black and white vinyl. Looked great.