Hello, I'm wondering if anyone can help. We had a plasterer do an awful job, then his boss came back and tidied it up, it was okish not perfect a bit lumpy. We now have damp in that area, and the second layer of plaster has come away from the wall, it appears that one of them has plastered over wallpaper. There was also a hole in the wall which hasn't been boarded, right in the corner by the skirting board, and now the plaster has come away you can see that they just plastered over the top of the hole, so there was nothing supporting the plaster.
The first layer of plaster is damp, but this must be because of rising damp or a leak as the plastering was finished 18months ago isnt it?
The damp is at about 1meter 20cm and its is in a corner where the original house joins onto an extension. The builder says it isn't his roof that is leaking and it is definately rising damp, (we have previously and a dampcourse) and he hasnt inspected the roof closely just looked at it from the back garden.
Has anyone got a professional opinion on this?

Plastering over wallpaper. Surely this was an accident.

The leak sounds like you may have an issue with the joint between the two walls. You could probably seal it with mastic.