erniee wrote:
I haven't seen any pink underlayment, either. Schluter systems makes an orange mat that can be used under tile. It looks like a waffle. Since this is probably a small area, I don't think the floor would flex that much. If it does, I'd get rid of the coach.
I just finished a 300sf tiling job in my house and used Schluter's Ditra (the orange stuff). The MINIMUM subfloor when using Ditra, is 3/4" plywood or OSB. The minimum subfloor when not using a decoupling membrane such as Ditra is 1 1/4". There are also maximum deflection requirements for tiling, and you would be surprised to see how little deflection a tile can take. Marble is one of the more sensitive tiles to cracking. It doesn't take much at all to crack a marble tile. The coach floor, while rigid enough for a vinyl product, is probably not 3/4" thick and is most certainly not 1 1/4" thick. Also, those required thickness numbers is combined with a 2x10 joist spaced at 16" on center. I can pretty much guarantee the coach is not constructed like that.
But, don't take my word, google tiling requirements (there is a tile association, I forget what it is called) and google Ditra. The installation instructions are available online.