My house has a 1/2 OSB subfloor on 2x10's 16" on center. I'm looking to add tile to our bathroom to replace some laminate. I'll be ripping out the particle board underlayment to get down to the sub floor. I confusing myself as to what I can do to get his ready for tile. Natural stone is the preference. There is a wall beneath the floor but is there a good way to tell if it's supporting the joists? If it is then my span is 9 feet which is ok per the deflection calculator. My next point of confusion is around the subfloor prep itself. Everything I see talks about 3/4 subfloor with a 1/2 ply underlayment for the natural stone. If I have a 1/2 subfloor, could I just put down 3/4 ply and not attach to the joists but screw to the subfloor?
I have another constraint which is the transition to the wood floors in the hall. The wood floors are 5/16 with a 5/8 ply underlayment on top of the 1/2 subfloor. I have wood floor transition pieces but the gap that would go over the tile is only 5/16 high so if I do a 3/4 underlayment, ditra, and tile then I'd end up 3/8 higher than that transition could handle. It would end up almost 3/4 of a transition. Is that to much? It might mean natural stone is probably now the best solution?
I've completely confused myself with this so any help would be appreciated. Thanks!