We've got a house built 1968. We've had a damp patch on and off but now appears worse. The area is around a window on a landing (window replaced 4 years ago), the plaster is begnining to crack and lift away. The recent heavy rainfalls appears to have created a really nasty frowsty smell (like a dead mouse...) in the hallway below - which also permeates into the kitchen - yuk!. We also had cavity wall insulation inserted about 15 years ago and wondered if this is now rotting in the wall although we cannot find any sign of ingress via the external wall or through roof.
We have no idea whether to contact a local builder/roofer/or????? hence the HELP
would be very grateful