January 12, 2009

Cob Construction - A Sustainable Way To Build

Though most visitors to Vancouver's Stanley Park may not be aware of this, the little mushroom-shaped concession hut located next to the park's miniature train ride is no ordinary Pacific Coast construction. A project of Down To Earth Building Bee, an organisation founded in 1996 to develop environmentally-friendly construction alternatives that would end the clear cutting of ancient temperate rainforests of the Pacific Northwest, and the Stanley Park Ecology Society, it is made using an architectural method referred to as Cob building.

Cob, the term originates from an Old English word that means lump or rounded mass, is a form of earth architecture that uses clay, sand, and straw as base materials. It has been used for centuries by many cultures. Rising lumber costs and environmental concerns have prompted a resurgence of interest in this form of construction, mainly in Britain and the Pacific Northwest in recent years. In British Columbia there is a growing number of cob houses, including several on the Gulf Islands, and on Vancouver Island, where in addition to a few already in existance, a 25-acre community is sheduled to be completed by 2010.

The fact that Cob architecture does not rely on synthetic materials and uses wood sparingly makes it not only environmentally sustainable, but also ideal for people with strong sensitivity to chemicals.

Despite the simplicity of cob, these buildings can be very durable, in Britain and France many are known to be still standing after being around for 500 years. They are relatively inexpensive and easy to construct, though this can be labourious and time consuming, particularly if done with the traditional method of using hands and feet to form the mixture. Fortunately, more modern techniques can be applied, including the use a rototiller to mix the building material. Innovations in the mixture itself are also being tried, such as the addition of pumice to provide improved insulation.

Currently, due to the fact that the resurgence of cob is a relatively recent phenomenon, gaining permission to construct a building of 100 square feet or greater in area can be a challenge. In B.C. cob falls under the alternative building materials section of building codes, which differ depending on town or municipality. It would seem that obtaining permission is generally a case-by-case process, more involving than that for a conventional construction project.