Hello
About 2 years ago we renovated our porch. It was always freezing cold in there so the tradesman suggested we line the walls internally with insulated plasterboard.
It was adhesively fixed to wall. Almost immediately a line of what appears to be damp / moisture appeared around the top of the wall, just below the coving.
The outer wall is a single skin of sandstone so I think that is porous and rather than being able to evaporate back through the stone moisture is appearing on the wall where the insulated plasterboard ends.
Ive tried drying out the room with a dehumidifier and it does improve but soon comes back.
Now I think it may be worth us sealing the outside stone work so moisture cannot penetrate through.
Would this be a good idea? Or is there another approach we should look at? Don’t want to take it all off!