The cause of damp in properties can be complex.
This particular house, with 18th century origins, is mostly of traditional timber frame construction with external walls partly made of solid brick and stone using soft lime based mortar. The physical damp proof course installed in most of the external walls, to prevent rising damp, is made of slate. The rear wall, made of stone, lacks a damp proof course but this is normal in a property of this age and type which were built without them.
Internal inspection revealed evidence of damp in the ground floor walls with high moisture meter readings and some damaged plaster. A horizontal tide mark was visible halfway up the walls, between the original and the renewed plaster, due to emerging efflorescent salts and moisture forced up from floor level and trying to escape.
Numerous uncorrected defects are likely responsible for causing damp inside. Modern impermeable plastic paint and hard cement mortar inappropriately applied upon the external walls and timbers which trap moisture and may cause damp. The external ground levels around wall perimeters were too high bridging the physical damp proof course and introducing moisture into the floors and walls. The rainwater fittings were also in poor condition likely leaking and causing damp inside.
There is evidence of a previous history of damp at the property. Damp remedial works have been undertaken which involved the insertion of a chemical injection damp proof course and the internal ground floor walls were replastered halfway down in a modern water proof type plaster.
This kind of damp treatment is expensive and may be considered inappropriate in older properties commonly constructed with traditional permeable materials which allow moisture to be absorbed and evaporated out harmlessly.
The waterproofing type of remedial work carried out did not cure the defects causing damp and may do more harm than good by trapping moisture in.
When dealing with old buildings, built with traditional materials, maintenance and repairs may be more costly because they should only be carried out by suitably qualified contractors experienced in working on older buildings. If not further damage may occur.