Do I need lime plaster for an older property or cob cottage in Devon?

If your property is a traditional Devon cob cottage, solid stone farmhouse, or pre-1919 Georgian or Victorian terrace in Exeter, lime plaster is generally required. These period properties were constructed without modern cavity walls or damp-proof courses, relying instead on high breathability to manage environmental moisture. Traditional lime plaster is vapour-permeable, allowing natural moisture within solid walls to evaporate harmlessly into the atmosphere rather than remaining trapped inside the core masonry.

Applying modern gypsum plaster or impermeable cement renders onto cob and solid stone walls frequently leads to severe structural and aesthetic failure. In Devon's humid South West climate, non-breathable materials trap damp behind the surface, causing the plaster to blow, decorative finishes to peel, and harmful mould to develop. On historic cob walls, trapped moisture softens the subsoil and straw structure over time, compromising structural stability. Lime plaster also provides natural flexibility, allowing the building to expand and settle through the seasons without brittle surface cracking.

Carrying out lime plastering involves a multi-coat system—usually an initial scratch coat, a floating coat, and a fine finishing coat—incorporating natural hair or fibres for tensile reinforcement. Because lime sets via carbonation rather than a rapid chemical reaction, each coat requires dedicated curing time between passes. When undertaking renovations on historic Devon properties or Grade II listed buildings, hire a specialist heritage plasterer experienced in hydraulic lime or lime putty, and finish surfaces with breathable paints such as limewash or mineral silicate coatings rather than vinyl emulsion.