I moved into my house a year ago, it had not been lived in or heated for over a year so there were small patches of damp in the house. Since then it has all cleared up apart from one room in the house, just under my bedroom window. I was away for a few days and when I came back the wall under the window was very damp and the paint and some plaster has come away. It is isolated to that one room/wall. Does anyone know what the problem might be and what sort of tradesperson could look at it?
