We have an internal wall in our lounge where the plaster has started to come off. Having stripped some of the top coat of plaster off the wall, and removed the socket, I've noticed that the socket backplate is rusty. Is this damp coming up from the floor (we have concrete floors, 1960's construction).
There is no damp on the other side of the wall (kitchen), and there is nothing above that could be leaking (the flaking plaster stops about 2 feet from the floor)