‘Brown is the new green’ says Sonoma County builder of homes of mud
Miguel Elliott still recalls walking through the Rancho Petaluma Adobe on a fourth grade field trip.
“It was a super-hot day but it was cool within the structured earth walls of the fort and I thought ‘wow.’ It just fascinated me that by using earth from right under your feet, you could build something that was still standing all these years later.”
Fast forward to the mid-1990s. After college, he saw a video about making homes with straw, water and dirt. He had found his calling.
“Earth is the constant, the most basic thing we have to build with. It all just resonated, and I resolved to dedicate my life to it,” he said.
That passion has taken Elliott around the world, from Argentina to Africa, Thailand to Guatemala and the U.S. developing his skills in natural building. He is the founder of Living Earth Structures in Petaluma. The mission of his business, founded in 2008, is to “construct high quality earthen structures using readily available resources, while encouraging community involvement through workshops and gatherings around the finished project.”
“Brown is the new green,” says Elliott, 50, who built a 120-square-foot cob house of his own on a ranch outside Sebastopol in west Sonoma County “Nothing is more sustainable. 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.”
“Cob” is a seventeenth century English word meaning “lump” or a rounded mass of earth. To combine its essential ingredients of sand, clay-rich soil, water and straw, the material rests on waterproof tarp or in a tub and mixed in a “cob dance.”
“Cob is such a fun material to work with,” he explains. “You are not limited to squares. Earthen walls can have rounded, sensual shapes. You can make a bench fit your body, fashion an armrest or headrest for yourself, or carve a design into the surface. Stomping on the cob to mix it gives you a foot massage! When sculpting with it, you are kind of massaging the earth back. It’s a nice energy exchange.”
Elliott frames his cob structures with wood uprights (post-and-beam) to support the roof and wood pallets between the uprights. Straw between the uprights serves as insulation and its all covered with the earthen plaster.
Sometimes he can forage materials right from the site, as he did with the “Cob on Wood” center, a homeless village built under an Oakland highway overpass in 2021. (The structures were subsequently moved from the Caltrans property to city property a few blocks away and will soon be moved again to a permanent tiny house village on Wood Street in Oakland, according to Elliott.)
As for the durability of the material, Elliot said the classroom cluster he built at Academy at the PARC in Sebring, Florida weathered two hurricanes without any issues.
“We bolted the cabins to the decks, used hurricane ties on the roof to keep them stabilized from the winds, and put a hydraulic lime plaster on the walls which helped to protect from the rains.”
Cob structures are best protected by what Elliot explains as the “hat, jacket and boots” strategy: wide roof eaves to protect the walls and an impervious foundation.
Cob construction code
Elliott said the North Bay’s recent years of destructive wildfires is leading some contractors to look at non-toxic materials like adobe, cob, straw bale and other fire-resistant building techniques as an alternative to “tinderbox-type construction.”
The Cob Research Institute, a 501(c)(3) nonprofit based in Berkeley, has produced the world’s first complete model building code for cob construction. After many years of intensive collaboration with several universities and testing facilities, as well as dozens of cob builders, engineers, architects, and code specialists, the code was added as an appendix to the 2021 International Residential Code by the International Code Council.
“It is possible to get a permit now to build a small accessory dwelling unit in your own back yard, but you have to use those engineer drawings that have been created,” Elliott says.
One of the structural engineers who worked on research for the Cob Construction Appendix — Anthony Dente of Verdant Structural Engineers out of Oakland — helped Elliott get drawings for the way he builds an ADU.
“I now have those drawings for a 200-square-foot accessory dwelling that could be submitted to a local building department to get a permit to construct one of my designs legally.”
‘Sir Cobalot’
Elliott lived for four years at the Isis Oasis Retreat Center in Geyserville in northern Sonoma County, where he built the Hobbit Hut, Gingerbread House and several other cob structures around the property.
