Mud walls may sound like a relic of the past, but natural builders say they could play a much bigger role in the future of American housing.
A new social media post featuring famed environmentalist Robin Greenfield points to a notable shift. Cob, the low-impact building material, is now recognized in a U.S. residential code appendix, potentially opening the door to more natural building projects.
What's happening?
Greenfield presents natural building as an ancestral way of creating shelter with simple materials, and the post describes the practice as low-toxicity. In the clip, he says, "All the materials we need to build natural homes are free and abundant around us."
According to the Instagram post, cob now appears in Appendix U of the 2021 International Residential Code. That does not automatically legalize cob in every jurisdiction, but it gives cities and counties a more defined framework if they choose to permit it.
The video also pointed to a wider range of natural building approaches already reflected in code appendixes, including hempcrete, light-straw clay, straw-bale construction, and monolithic cob.
One commenter celebrated the long tradition behind the practice, writing: "That's how our ancestors have built their homes. In Europe, Asia etc. Clay, lime, wood, straw, bamboo etc. It makes a healthy and wonderful living space."
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Why does it matter?
For many people, housing feels increasingly expensive, complicated, and disconnected from the materials around them. Natural building methods such as cob may appeal to some because they can reduce reliance on heavily processed materials while offering benefits mentioned in the post, including non-toxic construction and fire resistance.
One commenter pushed back on the idea that anyone can simply begin building, writing: "We can't build our own home, at least in LA County, due to building code, zoning, etc. It's illegal to live simply, naturally, and affordably like this."
When a method appears in code, it can be easier for builders, residents, and officials to treat it as a legitimate option and, in some cases, move it through permitting.
Homes built with earth-based or plant-based materials may also lower demand for more pollution-intensive products, especially when those materials are sourced locally.
That will obviously not be the right path for every homeowner or renter, but it offers another option as communities search for healthier and potentially lower-cost ways to build.
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