Cob buildings, along with any ancient buildings made from natural materials, need to breathe.  Lime and earth plasters and renders allow moisture to pass through them.  This is especially important where there is no damp proof course present. The inevitable damp that comes from the ground can escape through the porous lime plaster.

Much of the restoration work we do involves removing impervious cement render, which has, over a period of time, led to damp problems.  By replacing it with lime plaster, the wall can slowly dry out, improving both the health of the building and the living environment.

Cob is a mixture of clay-based subsoil and straw. The subsoil should consist of 10-30% clay and some form of aggregate. This is sometimes naturally present in the subsoil or can be added during the mixing process. There is a huge variation in the material used as cob in ancient buildings from almost topsoil to strong heavy clay.

Because of the malleable nature of cob it is particularly suitable for sculpture and creating organic shapes within buildings.  It is almost harder to make a straight wall than a curvy one. 

Another benefit of building with cob is its capacity as a thermal store. During the summer months the walls absorb heat then let it out when the temperature drops. It was often said of a cob house that it was warm in winter and cool in summer.  Many garden walls were built of cob because of its ability to let out heat and protect delicate fruit.