Sandstone is the main type of building stone used in Scotland. Although a durable material, sandstone is also naturally porous, making it prone to erosion if subjected to water and wind over time. Correctly used and maintained, however, stone is a sound, stable building material – as shown by our many prehistoric, medieval, Georgian and Victorian buildings.
Many stone decay problems begin with the failure to maintain buildings. Regular inspection and repair of roofing leadwork, rainwater goods and underground drainage will help to prevent water from entering and saturating stonework. You should also look out for pointing missing between individual stones, as moss, grasses, small bushes and saplings may begin to grow in these gaps, damaging the structure further.
Historic buildings are expected to show signs of ageing:
- sandstone can erode and decay to quite a depth before causing structural problems that must be fixed
- the surface patina that forms over time is very valuable, as it adds a sense of history and a protective layer, and it can also be attractive
Stone cleaning can remove the surface patina and lead to serious erosion. Both physical and chemical cleaning methods have caused severe damage to Scotland’s stone buildings in the past. As a result, stone cleaning is generally reserved only for very heavy soiling.
New cleaning techniques should also be treated with caution, although some are appropriate to use. The safest way to avoid the risk of damage to a sandstone building from any form of cleaning is simply not to clean in the first place.
When maintenance and repairs are needed, you should select a contractor who has the right technical knowledge, good craft skills and the ability to source and work with the right materials.