Damp grey cloud like patches on landing ceiling appear after all this rain we are having, can’t work out why as had a new roof and valley fitted 3 weeks ago,above ceiling is very small loft space, joists joined to the ceiling. Could it be bad ventilation or condensation? No leaks as such just very tacky damp patches. The roofers say it can’t be the valley however they did come and relead the chimney but not much improvement. Causing lots of stress trying to deal with it and getting nowhere! Any help would be much appreciated.