I wonder if you can provide some advice please?
We moved into a semi-detached Victorian property two years ago. There was damp in the rear first floor bedroom, with the party wall clearly visible from the second floor. It was in poor repair, with inadequate flashing. A roofer then did a good job of protecting the wall with felt and refitting all the flashing. I have no doubt that there is no leak.
But the damp in the bedroom did not dry out. A damp specialist suggested it was potentially hygroscopic so this year a plasterer replaced all the affected plaster.
Unfortunately, the damp has re-affected the new plaster.
Now I am puzzled as to why. One cause might be next door. The neighbour is elderly and her side is in poor repair - there is even a small buddleia growing. Before I cause them unnecessary concern, does anyone have experience of damp intruding from a next door property? Or can you think of another cause?