The house is built from stone and lime mortar around 1880. The exterior walls are plastered with an extremely hard cement render, which I will not be removing as it’s listed and there are lovely moulded features.
The interior is mostly lime plaster which I have removed, there are however patches of cement plaster inside, down low where there was signs of previous damp issues due to high ground level behind, I have not yet broke that off. Should I? The house is built on solid rock, but I did notice a small gathering of water under the floor when I dug it up, the floor was replaced with radon barrier, 150mm insulation and a 6 inch slab. There was a bad problem of dry rot due to a leaky roof, so I replaced the roof, all windows and doors, took all timber out of the walls.
My question is:
What interior insulation can I use that is cost effective? Because of the cement finish outside, lime is useless as it won’t breath? Can I dry line it with a 4 inch cavity and an insulated slab? Should I vent the cavity?