Posted on Oct. 14th, 2020

Of all the pandemic projects undertaken by kids under quarantine, the “Cobthedral” that three Santa Rosa boys built using dirt dug from their own property has to be one of the coolest. The round hut looks like a Hobbit house, with glass block and stained-glass windows, handy niches for storing stuff, and a living roof with succulents growing out of it. It playfully got its name because of its churchlike qualities. But it’s built to be the ultimate boy’s hideout, perfect for play, practicing on musical instruments, or working on projects.

And while they don’t have to travel to Middle Earth to get there, they certainly could pretend they slipped into some crack in the earth or wormhole and landed on a far-off planet or hidden world of dragons and sorcerers. Oliver Armstrong, 12, and twin brothers Alex and Galen Armstrong, 9, spent the last three months constructing their playhouse literally from the ground up. They dug the heavy clay soil, leaving a hole 5 feet deep to play in. They built the 125-square-foot cottage out of natural or reclaimed materials; primarily old packing pallets and a wet earthen material called cob. It was all under the direction of Miguel Elliott, an expert in building ovens, benches, walls, and other structures out of cob, an ancient building material that is a mixture of subsoil, water, and organic material like straw and sand if needed.

He calls his tiny houses “cobins,” and they have a multitude of uses in a home landscape, such as an art or writing studio, man cave, she shed or dog house. They are small enough to not require a building permit, although Elliott does have professionally engineered plans to build a larger, habitable accessory dwelling unit out of cob.

Transforming a ‘Dead Spot’

Elliott, fancifully known as Sir Cobalot, has been building cob structures for years, often overseeing them as group or community projects. But the “Palletable Cobin” is one of his newer ventures and poses intriguing possibilities for homeowners looking for a little extra living space. For Veronika Vuksich and Renee Armstrong, both physicians, it proved to be a great learning project for their three boys, who came home excited after Elliott visited The Sebastopol Charter School they attend to talk about building with cob. The boys already had been working on their backyard hole for several years and had a pile of dirt ready for a project.

“It wasn’t like I was looking for something for them to do. We had no idea how long this shelter period would be,” Vuksich said. “But it just became this wonderful opportunity, the silver lining.” They had a perfect location. “All we had here was a bunch of weeds and some logs,” Vuksich said. “We called it Flintstone furniture. We roasted some marshmallows there twice in the last 10 years. It was sort of a dead spot.” Elliott started by bringing in a load of gravel to level the space and create a building mound. Then they put in four-by-four posts 40-inches apart, the width of the pallets. They placed the pallets and stuffed them with straw for insulation. The next step was framing the shelves and windows. Then they covered the structure with a wet, mudlike cob mixture. And what kid doesn’t like to play with mud?

Over the earthen plaster they placed a hydraulic lime plaster, which sets with water and creates a highly durable structure, Elliott said. Natural hydraulic limes were used by the ancient Egyptians, Greeks and Romans, and many of those structures are still standing thousands of years later. He sources it through TransMineral USA, a Petaluma-based company that sells it all over the country. The cob can be sculpted before it dries. Elliott shaped it to look like the windows and rounded door are framed in wood. Vuksich also had a hand in the project and sculpted decorative symbols into the walls, like a Celtic Knot and an Egyptian ankh. The boys added decorative touches by embedding stones in the wall, as well as colored bottles and glass blocks for cool lighting effects. Even on a hot day, it remains cool inside the playhouse.

Cob on Maui

For his projects, Elliott tries to source as much of his soil as possible from the same site where he will be building. For the Armstrong boys’ cobin he got about 25% from their own yard (they wanted to keep some of their dirt for their own building projects). Sometimes the clay soil is strong enough as it is, but frequently it will require additional sand to create a buildable cob mixture. Elliott has been digging dirt and building with soil since he was a boy. He tried building his first cob structure in fourth grade – a kiva oven made of cob – after he saw several on field trips to the Petaluma Adobe and to a native Miwok village.

“I asked if I could build one on the school playground. So the next day I came to school with my pickax and shovel and dug a hole 4 feet deep and with willow branches made a dome,” he remembered. “Then it rained and filled the whole pit with water overnight.” That was the end of that project. But as an adult, Elliott spent a decade traveling the world learning about alternative building techniques and materials. He came back home to Sonoma County and started Cob on Maui in 2008. Building with used shipping pallets is one of his latest projects.

“It’s estimated that more than 20 million pallets are thrown away in America every year,” he said, explaining that the space between the slats is the ideal width for straw, an effective insulation material. “You can get used pallets behind stores. They’re often just giving them away. Or you see big piles of pallets on the side of they road that say ‘Please take.’ They’re one of the few building materials you can actually salvage for free, and you’re often doing businesses a favor by taking them.” Elliott lives in a series of tiny cobins in Sebastopol, each 120 square feet, with one used as a bedroom, one a kitchen and one a bathroom.

“Instead of doing conventionally framed houses with two-by-fours every 24 inches and fiberglass insulation, drywall, wood siding and paint, which is all costly and toxic, I simply use a pallet insulated with a straw fiber and cover it with earthen plaster, which is all free, healthy and natural,” Elliott said. The Armstrong boys are typical boys and have been building with dirt in their large backyard, an urban homestead with raised vegetable beds and a chicken coop. They’re starting to move into their new playhouse. Beside the window is a small desk where Oliver can do the things he loves – making maps and documenting the weather. Galen can’t wait to try out his new cello in the playhouse he helped build, which has great acoustics. Their moms plan to get them a pull-out couch, a comfy spot for reading. It’s electrically wired for lights and a space heater to make it toasty in winter.

“In their school they have to do building projects,” Vuksich said. “But they’ve gone way above and beyond the assignment.”