A thousand apologies if this has been answered elsewhere, but i DID search first and couldn't find the answer. ...i'm about to refurb my bathroom, floor to ceiling tiles approx 60cm x 40cm..It is already tiled so my first problem is likely to be how much damage i do to the existing plasterboard..Now i have had some advice from the guy at the tile shop who says i should use acrylic primer on the boards first ( which he kindly sold me ), and use powder mix cement based adhesive ( again which he sold me )..So far so good i hope please advise if not...Now on to my main concern.The grout in the old tiles inside my shower cracked ( after many years i might add ) and water got behind them and softened the ...wait for it...PLASTERBOARD..I know i know ...anyhow the tile shop man says that the new adhesive and grout will not do this as it is flexible , is he right ? And if so , is there any need to use Aquapanel board or can i just stick with plasterboard...All suggestions are greatly appreciated....Bill