Traditional renders and plasters were almost always lime based and therefore breathable. Under normal circumstances, older buildings will function well if they are allowed to work as they were intended.

Mortars, plasters, renders and finishes should all be made of lime and allow moisture to pass through and evaporate away. Cement, gypsum plaster and plastic paints are universally available and there are very few old buildings which have not had some modern materials applied to them. If your building has already been treated with modern materials watch the building carefully for any signs of problems.

Repairing lime based buildings with lime based materials can often solve many of these problems and will invariably prevent more from developing.