spaces sustain down home dirty
Image: Kurt Hettle

Whether out of necessity or a desire to be connected more closely to the earth, people from China to the American Southwest have built their homes with earthen floors for centuries. But in Portland, the floors’ recent surge in popularity comes from our dedication to living lighter on the land—and perhaps a bit of our “against the grain” mentality. After all, earthen floors are not only environmentally responsible—they’re also pretty different.

In medieval times, dirt floors were simply packed earth sealed with olive oil and a layer of straw for warmth. Today, the floors are a bit more sophisticated, made from a mixture of clay-rich dirt, masonry sand, straw, and water, which is then dried and sealed with a compound made of linseed oil and carnauba wax. They range in color from deep brown to vibrant orange or mellow blue, depending on the contents. You can stencil designs in them, add straw or shredded paper for texture, and play with iron oxides and white clay to change their hue. The floors can be as elaborate or as plain as you like.

Dave Heslam, president of Portland-based Coho Construction Services Inc, chose an earthen floor for his home in the Overlook neighborhood mainly for its sustainability. “Not only are the floors made from all-natural materials,” he says, “but they also have a lower embodied energy”—which means less energy is expended in the process of making the materials for the floor than would be spent on alternative flooring options. “Concrete, for example, is made with Portland cement, which is very labor intensive and takes a lot of energy to produce,” Heslam says. And since dirt stores heat well, the floors are also ideal for radiant heating, another energy-saving quality.

“I’ve seen some earthen floors last 25 years,” Heslam says. Plus, as he points out, “the oil makes the floor pretty stain-resistant.” He and his wife, Caitlin Campbell, have three kids under 3 years old—they would certainly know.

"Portland is a great market for earthen floors because it’s a creative, open-minded place that is willing to try new things.”

Sukita Crimmel of From These Hands (503-957-6132, sukita.com), a natural building company here in Portland, has installed eight earthen floors in the city and helped Heslam design his floor. “They are still a bit obscure,” she says. “But Portland is a great market for earthen floors because it’s a creative, open-minded place that is willing to try new things.”

Let us preface this tutorial by saying that, while we Portlanders are a handy bunch, you may want to hire a professional like Crimmel if you plan on redoing your entire first floor. Her company can help design and install an earthen floor from about $7 per square foot; prices increase with more complicated colors, patterns, and thicknesses.

On the other hand, if you have a sunroom or yoga studio that’s aching for a new floor (and can absorb a few imperfections), give it a shot yourself. But since each site has several factors affecting the formula, including type of dirt, humidity at the site, and additional contents, you should at least call Crimmel for advice or a full consultation before you start. Here are the basics.

Ready the Rigging

Earthen floors can be installed year-round, but the warmer, less humid summer months are ideal since the drying time can be reduced and there is no chance of a freeze. You can request earthen floors for all kinds of new construction, but if you are remodeling a room, have a contractor or engineer check your floors to be sure the existing joists can support the weight. The general rule is that if they’ll support concrete floors, they’ll support an earthen floor.

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.

Bring It Home

When it’s finally dry and finished, the floor—though much harder than natural dirt—has a softer feel than concrete, so it’s easier on your legs and feet. It also has more give, so in a one- to two-inch pour, it won’t crack as easily as concrete. If it does happen to get a blemish, simply mix up a small amount of the same materials you used before and smooth it over. Just be sure to seal the new area with the same vigor you used on the original floor. By adding a new coat of wax about every 10 years, you’ll have an attractive, sustainable floor that will warm up your space for decades.

Get to the Source

You can find everything you need for an earthen floor locally, but the most interesting ingredient to hunt for is the dirt itself. You need clay-rich soil to make the floor work, which means it needs to come from more than one foot deep. Try getting dirt from a cemetery. It may sound strange, but that’s where you’ll find some of the best dirt, because it comes from, well, six feet under.

Also try construction sites, places where postholes are being dug, or anywhere else where people dig below one foot. In most of these situations, you’ll either get the dirt for free or be charged only a nominal fee. Just call the caretaker or construction company beforehand.

STRAW: This can come from any farm-supply store, such as Burns Feed Store (29215 SE Orient Dr, Gresham, burnsfeed.hdweb.com), where you can buy a 50-pound bale for $5.

WASHED MASONRY SAND: Best Buy in Town (2200 NW Cornelius Pass Rd, Hillsboro, bestbuyintown.biz) sells sand by the yard. You can pick it up in your own container for $37 per yard or have it delivered for $79 for the first yard; the price per yard decreases with bulk. One unit, which is 7.4 yards, costs $279.

MORTAR MIXER: Interstate Rentals (1130 N Schmeer Rd, interstaterentals.net) rents mixers for $50 per day, plus a $200 deposit.

SEALER: You can find BioShield sealers at Ecohaus (819 SE Taylor St, ecohaus.com). A 2.5-liter bottle of Hard Oil (#9) costs $48.50; a 2.5-liter can of Resin Floor Finish (#4 or #44) costs $74.

BOOKS: Check out The Hand-Sculpted House (Chelsea Green Publishing, $35). Though the book takes a different approach to laying dirt floors than Crimmel does, it provides useful background and earthen building information.