Miguel Elliott, founder of Living Earth Structures in Petaluma, California. specializes in building with cob. Elliott has built over 250 cob structures around the world. His creations range from small ovens and benches to full-sized homes — each one is a unique work of art.
“Nothing is more sustainable,” Elliott says. “If you take a structure made of earthen, sun-dried material, protect it right with good sealer and a nice roof, it can last a long time. There are cob houses in England that are 700 years old, with many still being lived in.” A childhood visit to the Rancho Petaluma Adobe sparked Elliott’s passion for natural building. On a hot day, he was struck by how cool and comfortable the earthen walls felt.
Cob’s malleability allows for designs that are both functional and beautiful, with curved walls, built-in furniture, and sculptural details.
Cob homes are fire-resistant, energy-efficient, and can withstand extreme weather. Elliott’s classroom cluster in Florida survived two hurricanes unscathed thanks to smart design and durable lime plaster on the walls.
What’s more, cob building is affordable. “The great thing about such a project is that it doesn’t take a lot of money; the main investment is labor and the creative energy of the participants,” Elliott says.
He even envisions corporations sponsoring cob-building workshops as team-bonding experiences, with the finished structures donated to those in need.
As wildfires and other climate disasters become more frequent, the building industry is starting to take notice of sustainable materials like cob. The Cob Research Institute has even developed the first official building code for cob construction, making it easier for homeowners to get permits for cob dwellings.
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True, in the right circumstances, scale, and meticulous detailing, cob seems to be a viable technique. Not necessarily a quick or less labor intensive method but yes the mass and clay contents are great for some aspects. Some experience or at least experimentation is needed.
The material goes in really damp so the dry out phase needs to be substantially complete before a shelter coat applied . Too wet and shrinkage cracking may rear its head as well as potential structural creep ( plastic deformation) at points of stress. Also, in a humid environment black mold and efflorescence has been an issue on at least one project reported. Not that any method or material is immune.
Ventilation is needed, watch the plumbing detailing and site drainage, damproof coursing, and skirt height and, if mechanical cooling is needed/used probably keep a dehumidifier handy.
Cool concept, though I’m having trouble seeing how a cob building can survive a hurricane. Now I get that cob is probably fairly wind resistant, but the moisture from the driving rains and possible flooding would surely doom the material, especially because I read that cob can’t handle direct contact with water.
Moisture from the driving rains and possible flooding are short term events. Generally the cob is protected by a “good hat and pair of boots,” as the saying goes so such moisture will not have a chance to erode it. Also, more durable plasters are often employed.