On Jan 5, 11:57�pm, wrote:
In a typical bathroom floor tile installation you have the following
sequence:

Plywood subfloor, Thin-Set, Backerboard, Thin-Set, Tile/Grout.

If the grout is not perfectly sealed and the bathroom is heavily used
(with a lot of water on the floor), where does the water stop? �I know
Backerboard is water-damage-resistant, but I hear it can wick and
absorb water. �What are we relying on to keep the water from soaking
the plywood? �Is it just the thin-set?

hopefully concrete backerboad and use cement to seal all seams