Prepping floor for tiles

[crispy_wafer]

Bathroom on 1st floor...  What would be the recommended prep for tiles?  I'm actually trying to work out the height for the w/c frame, but as the finished floor will be tiles I'm trying to work backwards.  Do I need to install a ply or nomoreply layer above, if so what thickness would be advised please, or none at all and just a ditra mat?

 

Currently got this stuff on the floor, glued, nailed and screwed onto pozi's (another picture below).

 

Installed onto pozi's

[nod]

Some still use ply cement board etc

I use Ditra matting directly onto the deck 5 mil for mat and adhesive Then what ever tile your using the adhesive needs to be the same thickness