I have 4 pipes: 1x water, 2x waste and 1x capped gas. The two board solution is interesting. Ideally I want to lay the least amount of board possible (i.e. once at 40mm). But this will difficulties around the pipes.
DPM on the walls too instead of a plastic sheet then.
Removing the need for Ditra would save several hundred pounds. I guessing the foam acts as the decoupling between the two backer boards.
Given the price of Wedi, would going back to (cheaper) Marmox board do the same job? The specification seem very similar (if anything the Marmox seems stronger).
