We have a typical stone built, 2/300 year old, 2 up 2 down Cotswold cottage that is in a preservation area. Of the two downstairs rooms, the living room is bare stone walls and the kitchen has been plastered with a cement based plaster. The floor was replaced 25 years ago and at that time an underfloor membrane was put under the tiled floor. The cottage is not occupied full time. The cottage is built into a small mound so the outside of the kitchen wall has soil alongside it rising from about floor level at the front to about a metre at the back. The back of the cottage has a flagstone yard that abuts the rear wall at a height of circa 20 cm above the internal floor level.
The plaster in the kitchen on all the walls has blown significantly over the past 7 or 8 years resulting in large patches falling off. The worst problems are on the wall with the soil alongside it. An internal wall is equally affected but the blown patches are only in an area within 50cm of the floor
We have been given different opinions as to the issue as a whole and I believe that the problem has a number of facets: the outside soil and yard being above the floor line; the lack of permanent residence meaning the heat and ventilation is low; a cement plaster/base has been used etc.
So the advice I would appreciate is what is the cure? We have been advised that the whole room should be tanked from the outside (may require building approvals) using either French drains for the flagstone yard and a “rubber/bitumen” coating for the outside wall with the soil against it, lime plaster and lime based paint internally, or re-plaster with cement based plaster and keep the heating on at a higher temperature. I would be grateful for any advice that you can give to resolve the issue. Thanking you in anticipation