I've grown concerned my subfloor is inadequate for tiling, given I've seen a lot of different opinions and suggestions floating around online.
I have 3/4" GP Plytanium Dryply, tongue and groove. This is glued and screwed into my floor joists, which are doubled up 2x10 pine boards, which are also glued and screwed together. The unsupported span is a little less than 12'. The doubled up joists are 16" centers, so there's about 12-13" between joists. I also installed doubled up 2x10 braces between the joists. The joists are installed on both ends using joist hangers. They're also slightly notched to rest on the center sill beam. The braces are attached via hangers, as well.
So, my basic question is, do I need to add more plywood on top of the 3/4" already in place, or can I just go ahead and attach my Schluter Ditra and tile this floor? I bought the Ditra on sale, so I can always return it and go with Hardiebacker, if necessary.
I plan on using ceramic or porcelain tile, most likely the smaller 2x2, 3x3 or 4x4 tiles that come as a sheet. I've not decided on the tile yet, thus the options.