The following is an excerpt from our June 2015 newsletter Force of Nature:
Cob building has been used for well over 400 years and it might just be making a bit of a comeback. Cob construction is basically subsoil mixed with water and straw. No mold or forms are used and therefore cob structures can be a great variety of shapes. You get a lot of great curves with cob. Cob building doesn't require fancy tools (or even power tools) nor highly specific skills.
Built from the ground up, it is a labour intensive process but the materials are abundant and unlike most forms of building can usually found where you are building. Materials are not fired in a kiln or mined (excepting perhaps lime if used on external wall). Cob buildings then have a very low carbon footprint.
While cob buildings have a strong amount of thermal mass, they do not have strong insulation properties. For more on cob and insulation see here. Still, Cob can built in cold, damp climates and do very well. Cob is quite water resistant and wide roof eaves serve to protect the walls and sometimes a lime plaster is used to protect the walls. Cob walls are also fireproof which is why they are often used for ovens including the increasingly popular cob ovens sprouting up in communities. A cob fireplace in a cob house works well.
New cob homes were very rare in Europe for a number of years. In fact in a cob house completed in Ireland in 2004 was the first in over 100 years. With a growing interest in sustainable building, more are being built now and cob is being incorporated into natural and green building. For example, the company Sota Construction used cob (and straw) walls in their headquarters, garnering the most LEED points every awarded in the state of Pennsylvania.
There are cob buildings in Europe, Africa, the Middle East and the Americas. Maybe there is one near you. For more on how a cob house comes together, check out this video from CobWorks on a cob house built in British Columbia: