Fitting and design
Tanking a bathroom: what a proper system looks like
The short answer
Tiles and grout are not waterproof. The layer behind them is, and it only works if it is continuous with no unsealed junction.
Design decisions worth getting right
- 1
Corners, junctions and pipe penetrations need matched tapes and collars, a rolled-on membrane that stops at a corner is an open seam.
- 2
Boards, primer, membrane and adhesive should be a compatible system rather than a mix of whatever was on the van.
Your questions answered
Do I need to tank the whole room?
The shower zone always. Full-room tanking is normal for wet rooms and sensible where a floor is timber.
Is tile backer board enough on its own?
It is a good substrate, but the joints and fixings still need sealing to make the surface continuous.
Working out what is realistic in your space?
Room dimensions, the position of the window and where the waste leaves the building decide most of it. Send those and we can be specific.