Lime work should be finished with a vapour permeable paint, traditionally this would have been a limewash. Limewash has been and is still used throughout the world as a decorative and protective coating.Lime Wash and Painting-Suska Damp Proofing in Dublin. It was used on most buildings from humble agricultural barns through to high status buildings like castles and cathedrals. The Victorians preferred to see the stone or brickwork and so the tradition of limewashing began to die out but, if you look closely at old buildings, you can often see evidence of old plasters and limewash. There is a renewed interest in re-limewashing many buildings, including castles and churches, to help protect them. Limewash, because it is mildly antiseptic, was regularly used in agricultural buildings, and still is, this is probably where the idea comes from that ‘limewash needs doing annually’ which is not true, but it probably was done annually for this reason in certain buildings.
Limewash is usually made using a high calcium (fat) lime putty. It sets when exposed to Carbon Dioxide in the air. It has a flat, matt finish and a ‘depth’ which most modern paints lack. It reflects light and tends to ‘glow’ in sunlight. If it is pigmented, there is a tendency for slight color variation across the surface. This slight blotchy effect is quite normal and is generally considered to be part of its beauty.