Common Earth Walling Techniques
FIGURE2: COMMON EARTH WALLING TECHNIQUES
EARTH MIXES LAID IN-SITU
For these, the mix commonly contains clay, aggregate, straw and sometimes, as an incidental ingredient where the material has been trodden by animals, dung and urine. In some areas, chalk is a major ingredient. Just enough water needs to be added to enable the conglomerate to be thoroughly mixed, lifted into place, and consolidated into place by treading.
A - Unshuttered/Slow process
In this process, the mix is trodden in place in deep layers. A drying interval is required between each lift. The technique is found in most areas where earth buildings survive in significant numbers, but is the predominent earth walling type in South and South West England, Wales, the East Midlands, and Buckinghamshire.
Examples of regional terms are 'cob' (South and South West England), 'clob' (Cornwall), 'clom' and 'pridd' (Wales), 'mud' (East Midlands, Southern England, and Wales), 'clay' (East Midlands), Grid 'witchert' (Buckinghamshire). In parts of Scotland, a mix where small boulders are thrown in is known as 'clay and dab', 'cloy and bool', and 'Auchenhalrig work'.
B - Unshuttered / Quick process
Here, the mix is trodden in shallow layers. This technique is believed to be largely confined to the Solwoy Firth area (although isolated examples hove been discovered elsewhere), and is known in Cumbria as 'clay dabbins'. The thinner layers enabled the laying process to be continuous, without the need for c drying interval between lifts. The straw bed between each layer aided the drying process.
C - Shuttered Process
In this process, the mix is similar to that used in unshuttered insitu mixes. Its extent nationally is unknown, since it is difficult to identify unless the shuttering marks con be clearly seen after removal of the render coats. Nevertheless, it is believed to have had widespread, if not intense, use, probably becoming more common in the early 19th century.
In Scotland, some 'clay and bool'work was laid between shutters. Here, evenly sized boots were placed against the shuttering faces, and the spaces between filled with a relatively fine aggregate earth mix.