Walling made from local soil(s) mixed with straw, and built with or without shuttering. It was used extensively before c1850, in areas where the soil contained clay or chalk. Construction is in block, infill panel or monolithic form; here we concentrate on the latter. Techniques and their names vary regionally, and include cob (the South-West and East Midlands), clom (west Wales), clay dabbins (Cumbria) and wychert (Buckinghamshire).

Earth walling is often concealed behind brick, stone or render. Clues to its existence, however, can include the presence of a protective plinth, unusually thick walls and an absence externally of sharply defined corners in favour of gently rounded ones. 

Earth wall

Even defects that initially appear alarming can often be effectively repaired, although a structural engineer should be consulted where there is any doubt over the stability of a wall.

Surface repairs involve cutting back defective areas and, using oak pegs, non-ferrous metal or tile slips to provide a key, patching with new or reconstituted earth. Deeper deterioration will require the removal of decayed areas and infilling with pre-made earth blocks bedded in earth mortar.

Cracks can commonly be stitched making use of pre-cast earth lintels, or non-ferrous reinforcement bedded on edge. Associated grouting is employed, whereby remaining voids are filled with liquid mortar.

Local tradition should be respected. The application of a lime- or earth-based render and/or limewash externally will be suitable in many cases. Internally, the walls of houses traditionally had a mud or lime plaster coated with limewash or distemper. The use of impervious Portland cement renders including or excluding wire or metal lathing, gypsum plasters, waterproof masonry paints and modern emulsions should be avoided with earth buildings. Such materials prevent the walls from ‘breathing’. Moisture can become trapped in the fabric and lead to serious structural damage.