I want to fix plasterboard with insulation attached ('crunchy board'?) on to a single skin external brick wall using the dot and dab (?) method. The wall does had some damp coming in from outside which I have treated externally with Thompson's Water Seal.
Should I treat the inside surface of the brick wall with some sort of waterproofing before sticking on the plasterboard given that I can't use an internal polythene layer? Would this cause problems with condensation?
If I should/can waterproof, what product should/can I use? Is there one that is breathable?
Any help gratefully received.