The new shower tray is going to be a really tight fit so was thinking of bedding in the tray first then adding green plasterboard resting on the top of it (then tanking then tiling).
Would that be ok or is there a good reason I haven't thought of as to why the plasterboard needs to go behind the tray?
Would that be ok or is there a good reason I haven't thought of as to why the plasterboard needs to go behind the tray?