We got some work done a couple of years ago and i think the brick wall wan't dry enough for the dot dab at the time. It's now not fully fixed in places and i can bounce the plasterbaord off the wall.
How can i re-attach it?
I've used a stud finder to try and find some to no success, as i say i think it was dot dab - but it ain't worked!!
Other than taking the board off theres not a lot you can do apart from plugging and screwing right through into the brick in a few places just to stop any movement.
i think you have annswered your own question really. wet walls and plasterboard do not mix. for the best result take down board and render with sand and cement (muck) waterproofer if you need it. if it stays up you run the risk of any salts or damp eating the board.
if you cant aford it at the moment then do like dan said . good luck
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