Lime plasters are soft, flexible and breathable and they play an important role in controlling internal moisture levels, keeping historic buildings in good condition. Modern materials such as cement and gypsum plasters, on the other hand, are very hard, impervious and can trap water in masonry, timber or cobb walls.
Many older properties were built directly onto the earth without foundations or a damp proof course. They were constructed in such a way that allows moisture to both enter and leave the materials – the opposite of modern construction techniques and materials that are sealed against moisture. If older properties are unable to 'breathe' they can suffer from damp problems, causing mould, fungi, dry rot and wet rot, which can in turn lead to insect attack. Mould spores can be a particular problem for people who suffer with breathing difficulties such as asthma.
If you have damp issues in your property it is very important to at least get the ground floor breathing. This can be done by removing any modern materials and using lime plasters internally instead, ideally with lime render and pointing on the external walls as well.
Internal lime plasters are typically made from lime putty and aggregates with the addition of horse or cattle hair to reinforce the plaster and control shrinkage. It can be applied to many different backgrounds including masonry, brick, lath, reed, wood wool and fibre boards.
Lime plaster must not be sealed with modern paints or wallpaper as it needs to breathe so it is important to use a limewash or breathable paint, with limewash being the most breathable option. Limewashes and breathable paints are available in a wide range of colours and have a much softer, higher quality finish than synthetic paints. We can help you find suitable suppliers for these if required.