Hi, For over a year I’ve heard knocking coming from what I assumed are pipes within the wall cavity of my 3rd floor attic conversion flat. The knocking only happens when it’s pouring with rain and in the morning when direct sunlight is hitting the area at my bedroom window. The factor sent out a plumber last year, but without being here when it’s happening it’s very hard to diagnose. He looked over the entirety of my roof and could find nothing loose that’d be causing the noise and I got no answers. It’s driving me mad, I spent most of last summer and most rainy nights sleeping in my spare room. Can anyone offer any advice please? Thanks in advance Ashley