We have a ground floor extension with a flat roof. There is a damp area in the corner. The ceiling use to be wet but we had this fixed and so the ceiling is never wet anymore.The damp never gets any worse even in heavy rain but also doesn’t dry out. The Celcon bricks are exposed at present so we can see the damp. We don’t want to paint them until we are sure the issue is sorted. The rainwater also escapes into a gully in this corner. Any help would be much appreciated.