The workers, all members of Red Dirt Natural Builders, are building a demonstration wall attached to a farm shed at Carolina Central Community College. They're working with a technology so old it sounds like something out of a storybook: wattle and daub.
A durable mix of clay, sand and straw, wattle and daub is just one of the natural building arts that Red Dirt is working to revive. The fledgling company, comprised of four owner/crew members, builds with clay, bamboo, stone, wood, thatch, and salvaged materials.
In forming Red Dirt Builders, Mike Calhoun of Silk Hope, Jay Hamm of Chapel Hill, K.C. Kurtz of Saxapahaw, and Francisco Plaza of Durham, have combined their skills in conventional construction and their interest in the environment. The group is a rare Triangle example of a growing natural building movement that has gained adherents in western states, where adobe, solar-friendly construction, and other alternative building methods have become commonplace. (In North Carolina, few builders are experienced in natural building, and state building codes have no standards for structures made using natural techniques.)
The Red Dirt Builders all share the goal of reducing the waste stream and the use of modern building materials--many of which pose hazards to construction workers and residents. "We all have an interest in creating more sustainable systems," says Calhoun. "The way you live, the kind of place you live in, that's something that's very attainable."
State recycling officials report that byproducts from construction and demolition projects now account for almost one-third of what gets dumped into landfills every year. A typical new house in the Triangle generates three to five tons of waste in the form of leftover wood, roofing tiles, bricks and other materials (see "Wasting Away," The Independent, April 18-24).
Most new homes now also use large amounts of pressure-treated lumber, which contains arsenic and toxic heavy metals. Fiberglass, used almost universally for home insulation, releases tiny particles that can damage the lungs. And most plywood and sheathing products contain formaldehyde, which can be released as a gas into the air.
Supporters say natural building methods are far easier on the environment. The glues, resins, preservatives and other potentially toxic chemicals found in conventional structures are absent. And fossil fuels are not being burned for processing or transportation of materials.
"There's just a lot of embodied energy in your average 2-by-4," Calhoun says. "From harvesting, to milling, to shipping, to you picking it up at the lumber yard."
The Red Dirt Builders use materials that are renewable and locally available. Whenever possible, crew members dig and harvest construction materials on site. They sometimes work with salvaged and recycled wood, but Calhoun notes that gathering and cleaning such materials can be prohibitively time-consuming.
Instead, the crew focuses on waste wood: off-cuts from sawmills are plentiful, and often get burned up if no one salvages them. Cedar poles are a durable alternative to pressure-treated posts. Red Dirt crew members look for cedar that is harvested through selective cutting or other environmentally friendly methods, or alternately, left as waste when timber companies clear cut forests for other lumber. They also encourage clients to consider using bamboo, which grows locally and renews itself in four or five years--a fraction of the time needed to grow a harvestable tree.
For Red Dirt crew members, the reasons for building with natural materials are artistic as well as practical.
"I like to think of it as kind of like sculpting a house," Kurtz says. "It's pottery on a grand scale." Since nature works in curves, rounded corners, wall niches, built-in benches, and exposed wood and stone are among the specialties Red Dirt offers its clients.
The company's work ranges from rough-and-ready sheds to fine, high-end details, depending on what a client is ready to spend. Costwise, natural building can be a bargain, or merely comparable to other methods. Some owner-builders of cob houses--structures made from clay and sand that don't require wood or metal framing to hold them together--report spending as little as $10 a square foot, according to Daniel D. Chiras, author of "The Natural House." But as might be expected of age-old, low-tech techniques, natural building methods are labor-intensive and those costs can add up.
On the other hand, the cost of building materials can be literally dirt-cheap, Calhoun says. So the price tag for a naturally built home is "about the same, or slightly lower, than conventional methods if you're hiring someone to do the work," he says.
How durable is a naturally built house? More durable than you might imagine, Plaza says. "There's houses in England that have been continuously inhabited for over 500 years made with these methods."
One such practice, cob building, may be particularly well suited to North Carolina. The word cob comes from an Old English word meaning "loaf" or "lump." Cob is also known as monolithic adobe. While adobe builders form their soil mixture into bricks that dry in the desert sun, cob is stacked and shaped wet--a more realistic option in the humid Southeast. Lumps of clay, sand and straw are stacked and worked together to form thick, sturdy walls that can hold in the sun's heat.
With a generous roof overhang and a well-planned foundation--what Calhoun calls, "a good hat and a good pair of boots"--cob structures can stand the test of time. The straw in the mixture is thoroughly coated with clay, he says, making it resistant to rodents and decay. And the finished walls are fireproof.
Natural materials are also surprisingly versatile. "You can build anything out of clay," says Hamm, who is also an organic farmer. "Walls, bricks, ovens, floors, potentially even roofs. We utilize clay as a renewable resource." Excavations dug for ponds and foundation footings are a ready local source of the raw material. Another natural building staple, straw, is an agricultural by-product, Hamm points out, which many local farmers now burn in mass quantities rather than bale for re-use.
Red Dirt also builds with slip-straw--straw that is thoroughly coated with wet clay. The slurry is then tamped into forms, similar to the way concrete is poured. When the mix dries, it can be covered with an earth-plaster finish. The advantage of slip-straw, Hamm says, is that it insulates better then cob. So a successful solar earthen house might have some walls made out of slip straw and some of cob, for better insulation.
Right now, the Red Dirt Builders can only dream of building all-earthen houses in North Carolina. That's because state building codes currently have no specifications for natural techniques. Inspectors have no criteria for judging the structural stability of a cob wall, for example, or the "R-value" of slip-straw. In fact, they may not have even heard of such building methods.
Barry Gupton, chief code consultant for North Carolina's Department of Insurance--which overseas building safety--says a homeowner would definitely be breaking new ground with an earthen building in the Tar Heel state. "I know their local inspector wouldn't know anything about those materials," he says. "They would have to hire a designer that could lead the homeowner and building inspector through that process."
In many other states, natural building has come into its own as a legitimate part of the housing market. New Mexico, Oregon, and Massachusetts now have code provisions for natural methods ranging from traditional adobe and cob, to rammed-earth tire structures made from old tires packed with dirt and then mud-plastered. Alternative builders in those states are pioneering other experimental methods, as well, such as paper-crete, a mix of concrete and waste-paper, and structural bamboo, which is routinely used in many Asian countries.
Natural builders in other states have found that some municipalities are open to using code provisions developed outside their borders as guidelines for assessing the safety and feasibility of unfamiliar materials and methods. Red Dirt Builders say they are ready and willing to pitch in if anyone wants to take on the bureaucracy and get an earthen house built in North Carolina. "We'd like to be an instrument for bringing some of these codes to the area," Kurtz says.
In the meantime, the crew is working to expand its natural building expertise. Kurtz is focusing on thatch, the traditional art of woven roofing. Thatch can be made from various plant materials, tightly bundled and skillfully laid to make a roof that sheds water. And as it turns out, one of the most recommended materials--a water weed known as fragmitis--grows prolifically in local waterways.
Red Dirt Builders have also been busy constructing barns and sheds, and doing decorative work. The crew recently completed a decorative bamboo fence at Akai Hana sushi restaurant in Carrboro.
Natural building enthusiasts estimate that as many people now live in earthen structures as in conventional ones--if housing is viewed on a global scale. The Red Dirt Builders hope their work will serve as a model for environmentally friendly construction.
As Hamm says, "It's an affordable and appropriate way to create shelter, if you're willing to do the work yourself."
At the end of the month, the crew will put the finishing touches on a 16-foot round hut at Sustenance Farm in Chatham County. The hut, which will be used as a combination garden shed and studio space for the organic farm, is the product of many hands and numerous workshops in natural building over the years.
Standing between gardens and farmhouses in a grassy field, the hut overlooks a sheep pasture. The earth-colored walls are thick and gently sloped--easy to lean against as you sit on the built-in cob benches. From outside, the structure seems to rise naturally out of the North Carolina red clay. Inside, the room is cool and quiet. It feels as safe as a cave, but open to the surrounding farmland.
For information on natural building methods and resources, contact Red Dirt Natural Builders at (336) 376-3107 or e-mail red_dirt22@hot mail.com