Cob Cottages

It is the archetypal English country cottage, the birthplace of Thomas Hardy in Higher Bockhampton near Dorchester in Dorset with walls constructed of cob and with a roof of thatch. But what is cob?

There is evidence that cob was used as a building material in the 13th century, possibly devised as a variation of the wattle-and-daub style of construction, but it gained popularity in the late 18th and early 19th centuries as a reaction to the high cost of bricks, which were taxed at the time, and the lack of availability of stone in certain areas.

Traditionally, English cob was made by mixing the clay-based subsoil with sand, straw, and water and oxen were used to trample it down and mix it. As some English soils are heavily chalk based, cob made with significant amounts of chalk content is known as chalk cob or wychert. Unlike in adobe construction where dried blocks are used, in cob construction lumps of damp cob are compressed and shaped to form a continuous wall sitting on top of a stone foundation. Sometimes the mixture is trodden onto the wall by the builders, a process known as cobbing.

Each layer of cob would be allowed to dry naturally and then that part of the wall would be trimmed before the next course was built. Lintels for openings such as doors and windows would be set in place as the walls took shape. The pace of construction was dictated by the length of time it took to dry each course. Typically, cob cottages have very thick walls, usually around twenty-four inches thick, and the windows are correspondingly deep set. Like Hardy’s cottage many are roofed with thatch.

Cob has some properties that make it ideal for building. It is fireproof, although the addition of a flammable thatch roof does diminish that advantage, impervious to creepy crawlies, provides excellent insulation against fluctuations in temperature, keeping houses warm in the winter and cool in the summer, is cheap and environmentally-friendly because the base materials are abundant and requires little energy to process. Another plus is that if the building has outlived its use, the material is biodegradable.

However, not everything in the cob cottage garden is rosy. Cob has a low resistance to water, especially in its raw form, and without proper treatment can erode in intense or prolonged periods of wet weather. Although durable, cob requires regular maintenance to ensure the longevity of the structure. However, if well maintained and refreshed as necessary, cob cottages can last as long as structure built with more traditional materials, as Hardy’s cottage, built in 1800, demonstrates.