Lime render is central to successful maintenance and repair of traditional buildings.
Traditionally-constructed masonry buildings used permeable materials such as stone, brick or cob (dried earth) in conjunction with permeable mortars and sometimes renders to keep out the weather. Moisture is both freely absorbed by these materials and released by evaporation from their surface. Damp is kept under control and prevented from reaching the interior by the dept of the wall and by the rate of evaporation.
Any impermeable coating such as a paint, cement render or sealant inhibits the ability of the surface to breathe and prevents evaporation, causing damp in the interior, and in time it is inevitable that it will crack, flake off or break down, allowing further moisture penetration to compound the problems. Any attempts to weatherproof a traditional wall is therefore pointless. A permeable render provides far more effective protection.