Cob is a mixture of subsoil, straw and water. When these elements are combined together they can be used in various ways for building.

To achieve a successful building medium, the soil must be free of large stones and must have clay content as this, once dried, will harden and give the wall its strength. Straw is as important as the stalks will bind the soil together.

Barley straw is the most commonly used binder in the production of cob in Cornwall and the South West of England.

However, hay, reeds, pine needles, wheat straw, etc., can be used – the tradition was to build with whichever was locally available. Cob would originally have been mixed by the hooves of domestic cattle.

With all the ingredients distributed around a large pen or yard, the cattle would compress it as they moved around.

A commonly held idea is that ‘dung’ is a vital ingredient. Its inclusion is inevitable but not essential. This mixture would then be forked onto carts or directly onto a stone plinth and then built up in layers.

The previous day’s layer is pared back using an adze and reused.

It is difficult to calculate exactly how many, some cob structures were built without a stone plinth and, needless to say, these structures no longer exist having succumbed to low-level water penetration and ultimately leading to wall failure.