I'm replacing a fiberglass tub that has stress cracks in the floor which occasionally leak. I'm hoping to install a Sterling Ensemble (if I can get my hands on one - just returned two of them to HD in the last couple of weeks because of defects and shipping damages).
The existing tub is sitting on 1/2" plywood, which is supported by joists at 16" oc. The existing tub does not have a mortar bed but I am planning to use mortar when installing the new tub.
It looks like the bathroom floor was tiled after the tub was set, but I doubt that there's much in the way of underlayment under the tile. My guess is that the tile is sitting directly on the same 1/2" plywood that I can see under the old tub.
My question is: once I've removed the old tub, should I replace the 1/2" plywood with something stronger (like 5/8 or 3/4), or should I add a second layer of 1/2" on top of what is already there, or should I consider the existing 1/2" plywood good enough to support the new tub? I'm thinking that the tile gives me 1/8 or 3/16 to play with, but if I raise the new tub any higher than that, there will probably be a gap between the apron and the top of the tile.