I'm starting work on our new downstairs WC and want to tile the floor with 6mm porcelain decorative tiles my wife has found.
The subfloor is a mixture of original floor boards and ply over joists. See here:
It's pretty small, around 1.3m squared. There are some gaps around the outside edge and there is some very small differences in height between the boards, but only around 1mm or so. In general the floor is level.
I want to lay something under the tiles to:
A - provide separation between the subfloor and tiles
B - waterproof the floor
C - level out the minor unevenness
D - raise the overall height of the floor (around 10mm or so)
So my question is what is the best option. Screed? Backer board? Membrane?
Any thoughts or advice would be greatly appreciated.
Many thanks