I had a plasterer with 47 years of experience come to see our old stone farmhouse. In one room, the electrician has cut through the wall. Underneath the gypsum plaster is a layer of what the plasterer said was sand cement on top of the stone.
While describing what he could do, he mentioned taking it back to the sand cement, which he called the 'original' layer put on the stone. He would put wood insulation and then lime plaster on top of this.
This later confused me because I thought, and seem to find online, that sand cement is not breathable. I thought the whole point of the lime plaster was to help the inside of the house, and the stone wall, to breathe.
Another question is whether wood insulation is necessary - I want some type of insulation, but is wood being suggested for its breathability? I honestly don't care about its 'sustainability' - I would like what works best for breathability and for insulating the room.
I plan to ask him these questions as well, but it's great to get perspectives from other people not selling me something.
