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CRI's Cob Code Proposal

Approved for the 2021 International Residential Code

Cob is an ancient method of building with earth.

Clay-rich soil is mixed with water, straw, and often sand to a dough-like consistency and sculpted into walls while still wet. Under different names, the technique has been common for centuries throughout northern Europe and in parts of Asia, Africa, and the Americas. For example, there are more than 20,000 cob homes in the English county of Devon alone. Some of these homes are as much as 600 years old and still inhabited today.

In recent decades, cob has enjoyed a revival in North America, Britain, and elsewhere. The resurgence of interest is driven in part by the fact that cob is one of the most ecologically sensible ways to build a house. The materials are often available for low cost or free on or close to the building site. Cob can easily be sculpted into whimsical and curvilinear shapes, making each cob building a unique work of art.

However, no building codes for cob yet exist in North America.

This places the burden on everyone who wishes to build a cob home legally to convince their building officials that cob is safe.

The Cob Research Institute is a 501(c)3 non-profit organization founded in 2008. Our mission is to remove the legal obstacles to building with cob. Through a series of tests on soils, cob mixes, and assembly techniques, we aim to develop easy-to-follow standards for safe cob construction. Our ultimate goal is a code for cob that retains its character as a simple, ecologically sound building system.

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