A guide to adobe, cob and earth-sheltered homes.
Once upon a time people stayed with their houses. A person was born in a house, lived a life in that house, and died in that house. Then the children went on with the house, and so on, for generations. This is the great charm Europe holds for Americans. When we walk into an old French farmhouse or Tuscan villa, the big flat earth tiles under our feet show grooves that connect us to the person who made them hundreds of years ago. Our longing for just one thing in life to be, or seem to be, permanent is answered, and most of the unsteadiness and frailty of human life is banished outside thick earthen walls.
Earthen homes, even brand new ones, are timeless. But earthen homes are not as abundant in the United States today as mass produced houses that never will endure a family heritage, never will carry the stories of many generations. Most of these homes do not breathe; they contain formaldehyde and toxic glue. Their thin walls cannot radiate heat in winter and coolness in summer. They hold in their foundations the forests that were lost, the land that was mined, the energy that was used, and the pollution that was created to manufacture the materials of which they were made. If we value our forests and land and clean air, using the abundant earth to build homes is sensible and wise. It acknowledges our responsibility to future generations of people and other living residents of the planet.
There are myriad ways of putting up earthen walls. Archeologists believe we left our caves for homes whose walls were woven of twigs and covered with mud. Even today, builders called daubers use variations on this ancient handmade method. Now we often use technology to construct rammed earth and mix in other materials to construct earth ships and straw-earth hybrids. From the simplest adobe hut to the most sophisticated contemporary designs the possibilities for earthen homes keep expanding.
Fifty percent of the world’s population lives in earth houses today.
“My grandfather used to say that the earth was full of sound. He didn’t mean cars. He meant crickets, frogs, and the echo of stars colliding in the intensity of the crowded Milky Way. How fitting, how intelligent for man to build out of that sound, that music. Adobe repels the discordant and amplifies the balanced sounds and music of life, death, rebirth.” —Orlando Romero, from Adobe; Building and Living with Earth (Houghton Mifflin, 1994)
Adobe probably originated with the very earliest civilizations. Essentially soil, adobe contains a mixture of clay and water, made into blocks mortared with mud and covered with plaster or stucco. Some adobe contains straw or other plant material. Adobe bricks need an annual period of arid weather to dry, which is why the material is so common and has such a rich historical heritage in the American Southwest and other hot arid climates.
Cob buildings are handmade in the strictest sense. Cob is clay and sand—and often straw—mixed together to create a building material that dries rock-hard relatively quickly. Builders layer handfuls of cob on top of one another, shaping walls with their hands.
Oregon cob aficionado Ionto Evans, widely credited with bringing cob to the United States ten years ago, distinguishes traditional cob from Oregon cob: “Traditional cob has depended on mass, thickness of the walls, for strength. Traditional cob is not always made of the best materials. Because of lack of transportation, traditional cob builders use what’s under their feet. Traditional cob buildings can be found throughout the world.
“Oregon cob,” Evans says, “acknowledges that, at the moment, we have access to cheap transportation and this wonderful waste product called straw. Oregon cob is characterized by careful choice of materials and the use of curvilinear walls for strength.”
Basic bricks are so commonplace, it’s easy to overlook them as an earthen material. They are easy to use and have all the qualities of other earthen building materials—they are small solar collectors, and they are fireproof. Unlike adobe bricks, basic bricks are blocks of pure wet clay, and fired, not air-dried, at high temperatures. Before going to the kiln, the clay is cut into bars with wires and molded. People have been building with some kind of brick or other for thousands of years; before modern transportation, the color of the bricks matched the color of the land. Bricks are popular because of their fire-resistance, and they can be placed in appealing patterns. Brick floors are common in old farmhouses and cottages, and you’ll often find bricks in herringbone or woven patterns in outside floors and walkways. For floors and walkways you can lay pavers—thinner and less expensive than building bricks—on sand.
Using the earth to berm or shelter a home, which may be made out of any material, is another way to build with earth. An “underground” house has many of the same advantages as earthen building does—it reduces noise; it holds heat in winter; it stays cool in summer; it is fireproof. It is also weatherproof, has no foundation, and uses less material and labor to build.
If you have ever mourned the loss of a ridgeline to a house imposing its silhouette on the horizon, you will understand the wisdom of an underground house that blends into the land and follows its contours. There are two types of earth-sheltered houses. In the chambered house, a truly underground structure, the entire structure sits below the original grade. The bermed house, on the other hand, is built at or close to original grade with earth mounded or “bermed” against the outside walls. Bermed houses often have an earth roof, too.
Two names are associated with underground houses, Rob Roy and Malcolm Wells. According to Roy, who runs the Earthwood Building School, soil has a mass of as much as 1,300 pounds per cubic foot. As a result, underground temperatures remain fairly constant. In the winter, the ground temperature at a depth of ten feet is a fairly constant 45°F even if it is well below zero aboveground.
Wells is quoted whenever anyone brings up underground houses, inevitably associated with cold, damp, dark basements. Wells says, “An underground house has no more in common with a basement than a penthouse apartment has in common with a hot, dark, dusty attic.” In fact most underground and earth-bermed houses go out of their way to incorporate passive solar features that complement their inherent thermal mass temperature controls. Underground homes tend to orient south, face their whole front with glass, and usually incorporate skylights. As a result they can be even brighter and sunnier than traditional aboveground homes.