spaces sustain dirt floor diagram

Earthen floors are all about layering. Sukita Crimmel, a local earthen-floor specialist, suggests spreading the dirt mixture in several thin layers, which are followed by coatings of oil and wax that seal out moisture and harden the surface. Here’s the basic structure, starting at the bottom with the subfloor.

Mix Mastery

To create your floor material, you’ll need to rent a mortar mixer from a local tool rental store (see "Get to the Source" on page 5). Mix one part finely screened, clay-rich dirt (use a ⅛-inch screen and run the dirt through) with two parts masonry sand, and add water until the mixture has the consistency of cake batter. If you want the floor to have a bit of texture, add chopped-up straw or colored shredded paper (about ¼ the amount of dirt) to the mix before you spread. This is a little bit like cooking with your grandma; you just have to know when it looks right. So before you spread a layer of dirt across the entire area, test it out in the corner to make sure it’s not too runny and dries within about four or five days.

Spread Thin

Spread the mixture out in layers of about one inch thick with a steel trowel. Once each layer has dried enough to put pressure on it, use the trowel to press the material down again, smoothing it out further and bringing the clay content to the surface. You’ll need to allow each layer to dry completely before spreading the next (this might take four to five days). Before applying each additional layer, mist the dry layer to dampen it, which will help the layers adhere better to one another. Your final floor needs to be at least one inch deep, but can be thicker depending on what your space requires.

Seal the Deal

Once the mixture has been spread and leveled, wait for it to dry completely, which will take between 4 and 14 days depending on the weather and your floor’s ingredients. You can speed up the process with fans and a dehumidifier. When the top layer displays no moisture, Crimmel suggests waiting one more day to be sure it’s fully dry.

Once the dirt mixture is laid and dried, you’ll need to apply four to six coats of linseed oil with brushes or rollers to seal the floor. Crimmel recommends starting with BioShield Hard Oil #9 for the initial two layers and finishing the floor with two layers of BioShield’s Resin Floor Finish #4 or #44. These products contain carnauba wax, which is harder and dries faster than beeswax; also, it doesn’t create a film on the surface that you’ll need to buff out. When it’s finally dry and finished, the floor has a softer feel than concrete, so it’s easier on your legs and feet.