The Rennes area's clay soil gave rise to the construction technique known as cob, used to build houses, manors, kilns and washhouses for four centuries.
These frameless "raw" earth constructions sprang up with the emergence of rural houses in the 16th century and had admirable hydrothermic and sound insulation properties. The wet mixture of earth and straw rested on a stone base known as a "solin". The opening surrounds were sometimes made of stone, but wood was more commonly used (known as the "Carrée").