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Down-to-earth shelter

For Jan Sturman, building a cob cottage is a fundamental expression of the meaning of "home."

Jan Sturman is literally a down-to-earth builder. His prime medium is neither wood nor brick nor stone but the earth itself.

He creates in "cob," a thick pudding of blended clay and sand stiffened with bits of straw. Relying on his hands and sometimes feet, and in the absence of whining power tools, he raises and sculpts walls, ovens, nooks, and lofts into the elements of home.

And he does it all with the most abundant, cheap, and renewable materials on the planet, none of which, Sturman often reminds, require labels warning of toxicity.

"In the last few generations, the entire ethos of home building has been snatched away from us," Sturman says. "That once powerful way to bind a community together is now replaced by a collection of industries - from construction to energy to finance - which denude the planet and ultimately divide and indenture us with debt. Cob building returns a sanity to how a home should be created." That "sanity" comes in the form a relaxed pace, the help of friends and neighbors, and the conspicuous absence of a mortgage.

Sturman's riffs about cob may be motivated by evolutionary biology. He draws his inspiration to create with earth as much from obedience to his chromosomes as adherence to environmentally friendly precepts and common-sense economics.

Sturman and his partner, Suzanne Hale, spent a year building their cob home. "We worked compelled by this instinctual urge to make shelter," says Sturman. "This urge is strong; without shelter, we die. Our ancestors knew this. They shout through our genes: Shelter yourselves!"

The term cob is derived from an Old English root meaning "a lump or rounded mass." Workers in 15th-century Britain typically shaped wet clumps of the clay mixture into bread-loaf-sized pieces for easy stacking and mounding. Unlike adobe, the earthen sun-dried bricks popular in the American Southwest, cob is laid up wet and dries in place. Cob walls can bear great weight. That's because the straw acts as a binding agent, Sturman explains, which adds the increased structural integrity that clay and sand lack by themselves.

Sturman's own cob cottage in Shutesbury is a study in improvisation. Many windows were recycled from nearby restoration projects and embedded right into the cob walls. He hollowed out a slice of a massive hickory stump cut on the nearby campus of Amherst College and used it as a window frame. A carpenter by trade, the 33-year-old Sturman was able to salvage interesting and useful bits and pieces from many of his woodworking jobs.

In lieu of a poured concrete foundation and excavated basement, which he estimates would cost at least $10,000, Sturman simply had a backhoe dig a 5-foot-deep, 2-foot-wide trench around the perimeter of the to-be-built house. At his leisure, he then filled the trench with stray rocks and rubble from around the site.

"With the trench extending below the frost line, that gives a very fine and stable base upon which to build," Sturman says. It's the same method once commonly used for the foundations of barns and outbuildings, and it's similar to a technique American architect Frank Lloyd Wright used when building houses with modest budgets.

From the surrounding woods, Sturman selected trees and saplings with the perfect sweep and bend for rafters, joists, and railings. Many remain whole, simply debarked, sanded, and rubbed with oil.

The outside walls are finished with a buff-colored natural sand stucco while the inside has a smooth skin of white lime plaster. Even the ground floor is cob, smoothed flat and polished with linseed oil.

Lacking talent in drawing, the ability to think in the abstract, or the patience to sit too long at a desk, Sturman and Hale learned to design and build in motion. Shapes and spaces evolved as the house grew. "We began with no more than a few rough sketches mislaid after the foundations were dug, and our clay model soon melted in the rain," says Sturman.

The soon-to-be completed home - all 500 square feet of Hobbit-like shelter - checks in at a cost of less than $6,000. The home is part of the Sirius Community, described by Sturman as an eco-village based on the Findhorn community in Scotland. Since Sirius is a recognized nonprofit organization, real estate taxes are also removed from the equation. The only added expense will be the cost of a septic system, which Sturman has to install to comply with local building codes.

His original plan for plumbing the house included only a composting toilet and a hand pump to draw water from the well he dug on the property. However, the building inspector insisted he have a flush toilet, conventional running water, and a septic system.

Though the building is wired into new technology - a home computer and telephone answering machine are powered by the photovoltaic cells that provide electricity for the house - Sturman's methods are planted in centuries past. Some of the oldest, most durable and aesthetically attractive dwellings, many dating to the 15th century, in England, Wales, and Ireland are cob, he explains. The traditional village huts in parts of Sturman's native South Africa are a version of cob. "That picture-postcard look of an English cottage with a thatched roof and white-washed walls is often a cob building," he says. Many of Britain's "roughly elegant" inns and taverns - still standing after 300 years - are cob, a testament to the medium's strength and longevity.

"How many particle-board and 2-by-6 stick houses would you bet will last three centuries?" Sturman asks.

One attribute of cob construction that has remained consistent through the centuries is its adaptability. The proportions of clay, sand, and straw vary according to the fancies of individual builders and the availability of the materials. Combining the components can be a communal experience, with a dozen or more people slogging barefoot in a makeshift mixing pit. An old cement mixer works well, too. When working alone, Sturman prefers using small batches mixed by foot in plastic 5-gallon buckets.

Laying up the walls is a methodical, gentle procedure not unlike that of kids playing with sand castles at the beach but on a larger scale. "We didn't use any forms, just our hands, shaping and raising up about a foot high each day," says Sturman. "That's about perfect for correct drying." As for how much was built in a day, Sturman says it was determined by the number of daylight hours and volunteers at the site.

Traditional cob structures were once limited by the composition of native soils close at hand. Today, however, heavy equipment can cheaply transport the optimal kinds of sand and clay for the strongest cob walls.

"And for the clay, at least, you usually pay only for trucking. Most excavating contractors are all too willing to get rid of it," says Sturman. "And sand is very cheap, a negligible cost when compared with any building material." The same goes for straw, he says, which is readily available from farmers or through agricultural or farm-stock supply houses.

Another entry on cob's litany of blessings is flexibility. Additions and modifications can seamlessly join the main structure. On Sturman's cottage, for example, the local building inspector was not pleased at the original bathroom design - which was partially open to the central room - and insisted on an enclosure with separate doors and access.

No problem. With an ax, Sturman simply hacked a hole in the 18-inch-thick wall. A dainty bathroom then grew like a bloom on the side of the house. He finished the rough edges with cob and plaster, and hardly a scar remained.

If cob has a downside, it's abundant enthusiasm on the part of the rookie builder. The temptation is to overbuild and underestimate the time needed to finish. "Start with a small central structure designed in such a way as to lend itself to growing out," Sturman says.

Despite cob's many virtues - low cost, ease of construction, heat-retentive properties, and environmental friendliness - the technique is not quite ready for prime time, as far as many building inspectors are concerned. Although no known codes in New England prohibit cob construction, regulations designed for other materials and imposed on cob can cause some difficulty.

"Take R factors for insulation, for example," says Sturman. "For walls, most new construction requires a rating of R12 or R16, depending where you are." R factors measure the rate at which heat escapes through a wall. A typical 18-inch-thick cob wall rates only R7. But examining R factors alone is a one-dimensional and misleading analysis, Sturman says.

"The performance of cob, because of the great thermal mass, more than makes up for a lower R factor. Cob walls hold heat, whereas a stud-and-insulation wall does not," he says. The cob wall, therefore, becomes its own radiant heat source, which reduces the amount of energy needed to heat the structure. "Performance should be the only thing that counts," says Sturman, who heats his cob cottage with just one small wood stove.

Fire code considerations can be another sticking point, since cob is not yet part of some inspectors' legal vernacular. But objections based on fire-code ambiguities don't pass the laugh test, Sturman says. Many cob structures have safely incorporated fireplaces and masonry stoves within the walls themselves. "To suggest that a cob wall poses a fire hazard is ludicrous," says Sturman. A cob wall is impervious to flame and heat, in most instances, Sturman explains. He has an open-hearth bread oven on his patio built of the same cob mixture as his walls. "I burn oak firewood right inside, and it has not caught on fire yet," he says with a laugh.

For those seeking conventional financing, cob construction throws a curve ball at most loan officers. Mortgage specifications are more at ease with wooden studs, pink fiberglass insulation, and asphalt shingles, all installed by a licensed and insured contractor. But as long as the home has the blessing of the building inspector, mortgages are usually not an obstacle, according to Sturman. Yet with cob's low cost and high sweat-equity potential, a mortgage may be conspicuously absent from the to-do list. And that, says Sturman, is just the point.

The root of the word mortgage is not lost on Jan Sturman. It means "dead pledge," and "we would all do well to avoid one altogether," he says.