I took a small section off, it felt dry underneath.Hmm. Interesting thread. Did you try removing any plaster internally to look at whether the dampness continued into the wall or was just on the surface?
Absolutely. My plan to is to go back to brick on the walls either side of the chimney breast, and lime plaster a base coat, then likely a woodboard with skim. I just didn't want to touch it until ruling out/fixing any ingress. I'll give it a week with a heater/dehumidifier on it to get it properly dry, then a week for safety in case any other causes come to the fore, then get onto taking it all back(including removal of the hideous concrete render underneath the gypsum!).It looks from your photos like gypsum not lime, therefore modern not historical. I'd be pretty surprised if that amount of water was condensation but have you considered taking more plaster off and maybe replacing it with an insulating breathable plaster, some lime hemp maybe?
This photo still baffles me but might just be my eyes. Anyway I have questions which you might not be able to answer but I’ll give it a go!
Hard to say to be honest. The crawl space is too low for me at 6 foot to get across without risking going through the ceiling!This photo still baffles me but might just be my eyes. Anyway I have questions which you might not be able to answer but I’ll give it a go!
Is there leadwork coming all the way through the wall into the loft space at the back?
What’s the thing coming out of the rafters that looks like a white pipe?
Is all the black stuff hanging down failed felt? Are the slates above it definitely good?
Those are a sort of 'double' interlocking concrete tile and that's the side joint between tiles that would normally be hidden, the 'side overlap' is much greater than it appears because of that. A self-respecting workman* would have cut them so that the top course under the chimney didn't stick out like that.some kind of 'fluted' material beneath the left most tile