Feet on the Ground: Earthen Floors

Article Tools

Image Gallery

Print

E-mail

Comments

RSS

2. Lay a three-inch subfloor. This will provide thermal mass and should be something that replicates the properties of concrete, such as gravel or stone mixed with sand and clay soil. In home applications, the subfloor can be tamped with a floor tamper or plate compactor.

3. Create the mix. This should be part clay soil (which can be purchased if not available onsite), sand, and straw or polyester fiber, which can be purchased from concrete suppliers. To get the right mix, you must experiment with a test area of at least three feet by three feet. The mix should be strong enough that it is not powdery when it dries, and it must contain enough fiber so that there are no cracks. Apply the mixture with a trowel in a half- to three-quarter inch layer. The material should come off cleanly and easily as you move the trowel across the subfloor. If it sticks, there’s either too much clay or not enough moisture; if it won’t stick to the trowel, there’s either too much moisture or not enough clay.

4. Seal the floor. Linseed oil is the most common sealer for earthen floors. However, Bill Steen notes, boiled linseed oil contains solvents and is highly toxic, while eco-friendly linseed oil can be expensive. “As a compromise, we take raw linseed oil and put it in the sun in shallow pans covered with a piece of glass, leaving a tiny air space. The oil pre-oxidizes and dries faster. It’s called sun-thickened oil.”

Environmental and economical

Earthen floors are hardly new, of course. From the earliest times, people have used earth to form home floors. In the American Southwest, ox blood was mixed with the dirt for a stronger, more durable surface. For similar reasons, rural Japanese poured bath water, which contained oil from the bather’s skin, onto the unsealed floors. In India, ghee or clarified butter was used.

The ingredients in contemporary earthen floors vary according to region, but in North America, they generally consist of water, soil with clay content, sand, and chopped straw. The mix is then poured, troweled into place, and sealed with linseed oil after the floor has dried. Other factors, such as insects, radon, drainage, and temperature, determine the use of subfloor materials and insulation.

While fans sing the praises of durability, beauty, and comfort, earthen floors would barely warrant a second glance if it weren’t for one additional attribute: They are just about as eco-friendly as building material gets. Robert Bolman, a Eugene, Oregon, builder, recently made local newspaper headlines when word of the earthen floors in his urban home and rental properties spread. Bolman, who learned to make the floors under the Steens, says they exemplify the natural building ideal.

RSS | Comments | E-mail | Print