Unbaked earth is one of oldest building materials. Half of the worlds’ buildings are built with unfired earth. Used in Ireland and UK in pre-historic times.  Cob was the norm in Britain in 15th century especially in the southwest of England and Wales. There are over 40,000 cob buildings in Devon alone.  Australia has a heritage of earth building as has the Americas, the Middle East and Asia. There are more than 90 million earthen structures in China. Cob walled construction has been used for hundreds of years in Ireland particularly in rural areas. This ancient technology has served as homes to Irish families for many generations. The attitude in Ireland has been (although gradually changing) that they are associated with our peasant ancestry and poverty. Whereas, in the UK there is a different attitude to these cob houses, where they command very high market prices.

From an environmental perspective these houses make sense – the earth is non-toxic and recyclable, does not contribute to pollution, and has no chemical toxins that are part of our modern buildings. Hardly anyone has an ancestor who hasn’t lived in an earthen home.

Most earth buildings are simple but many are elaborate temples, churches and palaces; some of which are still standing today. During the 20th century public opinion started viewing cob structures as snug, historical and picturesque and so created a revival. In 1999 there were 40 new cob structures in Britian alone.  

Cob building offers flexibility of design allowing curved walls with ease. Walls are ‘breathable’ creating a comfortable and healthy indoor space, supporting environmental balance and health.

Methods

• Adobe – dried brick of earth and straw 
• Wattle and Daub – roughly applied plaster straw or mud
• Cob –  mix of clay, straw and water made in ‘loaves’
• PISE (rammed earth) – earth tampered in shuttering

Reasons to Build with Earth 

• Construction is simple and safe.
• Owners can more easily participate in the construction of their own dwelling.  
• It is empowering . 
• It is a monolithic construction with high thermal mass.
• Environmental reasons 
• Building with cob is a peaceful and rhythmic exercise
• Facilitates irregular spaces easily
• Cob is ideal for creating sculptured decoration and furniture 
• As it is fireproof, cob can be used for building ovens, stoves and chimneys. 
• Earth walls are very good regulators of internal  temperature and air quality. 
• Materials needed, are easily accessed, perhaps on site.
• Financial Empowerment
• Durability

All biological materials have a predictably short life. Wooden structures generally survive only a few generations.

Currently we used fast grown softwood where a house is in poor shape after 50y ears. Earth by contrast, being geological, lasts indefinitely. Inhabited earthen buildings in the Middle East and India are often more than a 1000 years old – 40 generations.

Comfort/Health

Cob buildings are warm and dry. Cob walls, generally 300-600mm thick,  provide immense thermal mass, ideal for passive solar construction.  Cob structures require little additional heating in winter and remain cool and comfortable on hot summer days.  

• Walls are ‘breathable’ i.e. allows the passage of water vapour. 
• Poor transmitter of sound
• Inflammable

Where Earth may not  be appropriate

• Irregularly heated buildings in colder climates i.e. churches, meeting halls etc
• On north slopes/cold sites with little sun access
• In flood plain