Interesting thread on liquid membrane.
If im not boarding the walls, i insist on the builder leaving them as they are, no skim or jointing tape, just bare plaster. i use a liquid membrane and corner taps, pipe collars etc...
i worked in Norway for a while, all bathrooms i worked on were finished with plasterboard and tanked with liquid - schoenox was the brand we used. very thick but brilliant to work with, even tanked inside the plasterboard box section that was to house the geberit frame for toilets and basins. No cowboys out there, bathroom specs are controlled by the insurance companies. No ticket....no tanking!!