I have an house constructed from old farm buildings. We have persistant damp problems in one or two areas of the house. Its generally a plastered wall, we have had back the guy who did the damp proofing a few times. He tested the wall and stated the wall got damper higher up. We called in the roofer who found nothing.
I than ran into somebody who said it was salt within the wall migrating to the surface of the wall. The salt was such that it attracted mosture out of the air causing the damp patches. Internally the wall is day, its only the surfaec that is damp.
Has anybody else run into this?
Also; what do I do about it? I was told to strip the plaster and replaster with some special kind of plaster that blocks the salt migration. What kind of plaster do I need to use? How well does it work?
I have been given quite a bit of duff advice from "experts" over the years, so I want to hear what the group thinks.