Cob Buildings 

 

Background: 

• Numerous cob buildings found in Devon and Cornwall are well over 500 years old.  

• Locally Tuinhuis at the houses of parliament in Cape Town is over 300 years old.  

• No complicated machines or tools are required, simply lots of labour and only very basic skills. 

 

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Benefits:  

• This material is a very durable form of earth construction. 

• Cob has higher tensile strength than other types of earth construction, which in general is weak in tension.  

• Offering relatively good levels of thermal comfort with a high level of thermal mass and humidity exchange. 

• Mixing and building with cob is very simple and easy to work with. 

• It requires no specialist tools. 

• Is well suited to community participation. 

• Materials can often be sourced from the site itself saving on transport costs.  

• It is also extremely versatile due to its sculptural qualities and is often used in combination with other natural building methods, like straw bale and sand bag wattle and daub etc. 

 

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Technical information:  

• A mixture of clay, straw and sand is mixed together into a stiff consistency and packed directly onto a masonry plinth wall. 

• The straw acts as reinforcing and while the compacted earth and sand mix create the compressive strength. 

• While cob can be mixed manually this process is very slow. Various forms of mechanization can be employed to greatly speed up the mixing process. 

• The walls need to dry sufficiently as they are built to avoid slumping, so generally one can only built about 300mm a day. 

 

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Company Track record/examples of work: 

• House Ashmole - 2009-2010, Stellenbosch 

• House Perry - Masepumalela informal settlement, Kommetjie, Cape Peninsular, 2007 

• House Brodie - Scarbourgh, 2003 

• Community Edu-care for Flower Valley Conservation Trust - Gansbaai, Western Cape, 2002 

• Note that all straw bale projects undertaken 1998 – 2024, have incorporated elements of cob construction