Hello, In our dining room in the top corner, there is a big damp patch that spreads all the way down to the floor on one side (internal) and to the bay window on the other (external). The internal wall has been boarded and skimmed on the other side (yet to be painted) - there are damp patches where it has been dot and dabbed lower down. I think the situation is best described in a list: 1. 19th Century house purchased 20 months ago 2. This damp patch existed then (there were many more - this is the last problem) 3. House skimmed/re-plastered just over a year ago 4. Walls in dining room were painted maybe a month after skimming (not a good idea as still damp), the other side of internal wall is unpainted and has damp patches where dot and dabbed. 5. This other side is single-storey and there is a pitched roof above it that runs down to this damp top corner 6. This roof was re-felted, tiled and leaded around 6 months ago (I have taken up a tile that butts up to the damp corner while it has been raining and it is dry underneath) 7. The whole house was re-rendered around 4 months ago (curing other damp problems) I would love some advice on where to go with this. Although I don't see where water can be getting in now, I can't confirm it isn't. The wall does not appear to be drying out at all. I'm a bit lost at what to do next other than hacking off the plaster and seeing if the wall will then dry out. I'm thinking of buying a damp meter to help keep track of it. Any advice on what to do next? Thank you!