Earth has been used in construction in one way or another for thousands of years all over the world. And it offers great potential as a sustainable building material for the future. Its use in traditional construction was common practice in Scotland until relatively recently.
A significant number of historic earth and clay structures still survive. But in Scotland today, you’re most likely to come across earth in the form of clay mortar, used to build masonry walls and as a surface finish.
Earth and clay materials share certain characteristics but can vary hugely in their composition. This is largely due to regional and local differences in local subsoil conditions. Subsoils vary in their ratios of clays and aggregates such as sands, gravels and silts.
Earth construction in Scotland varied regionally according to the materials that were available locally. Earth has been used on its own, and with lime, timber, straw and stone, to build structures suited to a wide range of locations and climates.
The use of lime was often employed to protect or disguise earth structures. The outside face was often finished using a thin lime harling or limewash. Where clay was used as a bedding material for masonry, the wall was often pointed in lime mortar.
Water is the main threat to earth and clay structures and clay-bonded buildings. Regular maintenance will help you to ensure that water doesn’t enter the building fabric.
To properly plan earth and clay repairs, it’s vital to understand the construction type and the composition of the original materials. Repairs to the earth structure or clay mortar should be made only once the cause of the underlying problem has been fixed.
If replacing an earth or clay material is unavoidable, any replacement material used should match the original as closely as possible.