An ancient adobe-like material noted for its strength and durability, cob is experiencing a 21st-century resurgence as builders and architects search for sustainable and budget-friendly techniques.
Spearheaded by David Reed of Texas Natural Builders, Houston’s first cob structure is currently taking shape out of clay, sand and straw at the Real School — an unschooling organization located within the Alliance for Cooperative Transformation’s property just east of the Museum District.
The 120 square foot building will serve as a multi-purpose space, with functions varying from a playroom to a meeting space.
The building’s design was adapted and elaborated from natural building movement guru John Fordice’s Solar Oval plan. The simple structure will include an exterior cob bench, a built-in desk, and cabinet space along the back wall.
“Cob,” an English term meaning "loaf," is used to describe mud-building, a time-tested method used not only in the British Isles but throughout Europe, the Middle East, India, China, equatorial Africa and the American Southwest.
This cob structure in Devon, England built in 1539, testifies to the material’s longevity.
Reed’s roots in traditional construction run deep — he’s worked as a home builder for the past 24 years. Motivated by the birth of his daughters and the desire to see them grow up healthy and self-sufficient, he’s transitioned to natural, sustainable and reusable building practices in recent years.
With hands-on training from contacts in the natural building community in locales as varied as Austin, Amarillo and South Dakota, Reed continually works to hone the craft of building earth structures.
As with many construction processes, cob building begins with digging. For this structure, volunteers started by creating a trench approximately 14 inches deep and 14 inches wide.
They then filled the trench with crushed brick from a local reuse center, which acts as a foundation stabilizer and allows any water to exit and percolate into the surrounding grate.
Broken concrete from local demolition projects finds reuse as the building’s stem wall, which rises approximately 14 inches from the ground and creates a break between the soil and the structure.
Mortar is used to adhere the broken concrete.
Volunteers sift rocks from the clay-based soil dug out of the trench. This material will be mixed with sand and straw to create the shed’s thick, earthen walls, which will measure eight feet in height.
Students and families from the Real School have participated in the construction process alongside a core group of committed volunteers from Houston Free Thinkers.
Lisa Chandler Delaune of the Real School notes that the project was of particular interest, as it “coincides with our philosophy of community-based learning.”
After sifting, materials are mixed while wet, by foot or with a machine. Houston cob structure volunteers opt for the former technique.
Four bales of straw purchased from a local feed store in Magnolia provide the building’s insulation. Wheat, oat, barley or rice straw stalk offer excellent alternative sources of insulation when packed into a cavity, as they have a high thermal variant.
Those interested in hands-on building are encouraged to contact David Reed via Texas Natural Builders' Facebook page or the City of Houston Cob Structure page — the friendly group welcomes volunteers and visitors, and anticipate working on the project into August.
The cobbers also need additional materials — flagstone, plumbing, gutter and solar equipment.
