A bedroom I want to redecorate is in an extension which was built about 20 years ago. I started stripping the old wallpaper off and underneath, I find that the previous owner plastered the walls with grey plaster and then painted emulsion directly onto the plaster. Unfortunately one of the walls is very slightly damp, i.e., the grey plaster looks noticeably darker in the slightly damp areas than the really dry areas. And in the slightly damp areas, the emulsion is blistering (perhaps due to me pulling the old wallpaper off) and in those places, the emulsion is fairly easy to peel off.
What would be the best way to approach redecorating this room? Should I attempt to get all of the old emulsion off? I hope I can avoid that extremely arduous chore.
Could I just peel the loosest of the emulsion off, and then paint the slightly damp areas with damp block, and then repaint the whole room in emulsion?
I'd prefer to end up with painted walls rather than papered walls.
I recall a similar situation in my previous house, and a builder commented that "they used the wrong plaster" (i.e., it was absorbing moisture more than if they'd used the correct plaster). I think I painted the walls with damp block and then top-coated with emulsion, and the result was surprisingly satisfactory. I didn't get any blistering or mildew appearing even ten years later when I sold the house. So perhaps I should use the same approach in this house. I'd appreciate your comments.
It's is verry difficult to determine the cause of the dampness. It could be penetrating damp, althought the walls do have cavities. I don't want to go to any great lengths to find the cause; I'd rather just paint over it and seal it in!