We considered having a wet room with the usual "flat floor walk in shower" but because it was located on the groud floor concrete floor (and would need to be kango'd) I bottled out and just raised the floor as a step up.
The main floor is below ground by six inches so is already semi tanked anyway and I worried digging it out may have cause water ingress.
Not as elegant I know but thought it worth sharing the alternative.
We already had bought the floor drain and supposedly it was going to collect everything on the floor in the room. But now we raised the shower floor the drain has become part of the shower install.
The main floor has no drain so the water just has to dry off naturally like a standard bathroom.
I know its not the answer to your question but I thought I would post it up to give others so alteratives for wet rooms where you just cant get the plumbing down low enough.
PS: once we decided on this compromise it cut down the labour, the costs and the materials. I guess its still cheating and not a "Flat level wet room"
