I had a somewhat similar problem in my lathe and plaster cottage near Edinburgh. It was last 'updated' after WW1 in the 1920's when the lathe and plaster had been fitted along with the wooden floors.
What I found was an excess of ventilation below the wooden floors such that in using a small drill to find the studs some 50+ years ago, every time I took the drill out a puff of plaster dust came with it.
In the end I had to bite the bullet and take down all the lathe and plaster on each external wall - making sure that the skirtings was off first and plywood jammed in the make sure that all the tails of the plaster didn't fall below the floor level and bridge dampness to the joist ends.
I used blocks of fibreglass insulation as far as I can remember, but one the things that I also made sure of was that I put up a 'damproof course' of polythene pinnned to the studs to make sure that there was no room moisture getting to the insulation and and creating dampness due to the dewpoint being reached.
As an extension to this story of this cottage, it was only in relatively recent years that I spotted that the stonework in my attic indicated that the cottage had originally been thatched - the angle of thatching is something well over the angle of a slated roof. I projected the angle down and it comfirmed something that had always puzzled me that the wall heads showed additional stonework had been added at some point.
What I found was an excess of ventilation below the wooden floors such that in using a small drill to find the studs some 50+ years ago, every time I took the drill out a puff of plaster dust came with it.
In the end I had to bite the bullet and take down all the lathe and plaster on each external wall - making sure that the skirtings was off first and plywood jammed in the make sure that all the tails of the plaster didn't fall below the floor level and bridge dampness to the joist ends.
I used blocks of fibreglass insulation as far as I can remember, but one the things that I also made sure of was that I put up a 'damproof course' of polythene pinnned to the studs to make sure that there was no room moisture getting to the insulation and and creating dampness due to the dewpoint being reached.
As an extension to this story of this cottage, it was only in relatively recent years that I spotted that the stonework in my attic indicated that the cottage had originally been thatched - the angle of thatching is something well over the angle of a slated roof. I projected the angle down and it comfirmed something that had always puzzled me that the wall heads showed additional stonework had been added at some point.
