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Code and permits

Cob entered the International Residential Code in 2021. What that actually means, and the call to make to your building department.

Cob is in the building code now

For most of the last century, building a cob house in the United States meant building without a permit and hoping, or paying an engineer to justify a one-off approval. That changed.

The Cob Research Institute’s proposal, RB299-19, Appendix U: Cob Construction (Monolithic Adobe), was approved by a 93 to 6 vote of attending ICC voting members, mostly building and fire officials, at the International Code Council’s Public Comment Hearings in Las Vegas on 26 October 2019. It then passed the online governmental consensus vote by more than the required two-thirds, and appears in the 2021 International Residential Code.

There is now a prescriptive code path for cob. That is the whole difference.

The distinction that trips everyone up

Approved in the ICC process is not the same as adopted by your jurisdiction. The ICC publishes model codes; states and counties choose what to adopt, and appendices are usually opt-in even where the main code is adopted.

So the question is not “is cob legal in America?” It is:

Has my jurisdiction adopted the 2021 IRC, and has it adopted Appendix U?

That is a phone call to your building department. It is the single highest-value first step for anyone considering earthen construction, and it costs nothing.

What to ask

Keep it short and factual. You are asking about adoption status, not asking permission.

1. Which edition of the International Residential Code has this jurisdiction adopted?
2. Have any appendices been adopted? Specifically Appendix U, Cob Construction?
3. If Appendix U has not been adopted, what is the process for a proposal to be considered?
4. If it will not be adopted, will you accept an application under the alternative materials and methods provision?

That last question matters. The Cob Research Institute notes that even before Appendix U is adopted locally, its publication helps a great deal when applying through the alternative materials and methods route, which is how most permitted cob buildings in the US have been approved. The appendix gives an official something published to point at.

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