I'm working on a bathroom that has considerable rot in the shower area. As I've proceeded to remove the bad material I've discovered the floors are concrete and are laid on top of plywood subfloor (this is a second story unit in a multi-unit building). The concrete ends at the walls so it appears the floors were poured after the walls were in. and the wall plates for the studs arewhat looks like two 2x4's that rest on the plywood subfloor. How do I get all the rotted subfloor out and replaced without dismantling all the walls.:confused:
Gypsum concrete has often been poured over existing or new plywood floors to level them and to provide larger sound and fire resistance ratings. It is easier to remove than concrete. Perhaps a google search would provide some ideas.
The National Tile Contractors Association (NTCA) has compiled a list of unsuitable floor tile substrates. "The questionable list also names gypsum concrete. Although problems may occur, methods have been devised to allow for satisfactory ceramic tile installations. You may use a sheet membrane for isolating your tile, or use a water-free urethane adhesive that will not affect the gypsum concrete. Just be sure you choose products approved by the manufacturer for use over gypsum concrete."
Removal of the subfloor is a structural matter which requires professional assistance. Don't expose yourself to any unecessary liability.