Damp has appeared randomly on one internal bedroom wall - about 1m up from the floor, all along a length of about 5m of wall. It doesn't appear to be rising damp (we think) as it doesn't start from the floor, but it's closer to the bottom rather than the top of the wall so we can't figure out how it could be coming from the roof. On top of this bedroom wall externally, there is a roof so wondering if it's being caused by that. Any ideas? Not sure which specialists to get in to fix it, as not sure what it is.
