Finishing an Earthen Floor with Natural Oils

Earthen floors have gained ground over the last two decades alongside straw bale, cob, and natural building generally. They remain a niche, but the technique is not remotely new. Variations exist all over the world, and nearly all of them come down to the same three materials: sand, clay soil, and fiber.

Traditionally built earthen floors in the southwestern United States were often finished with ox blood, which is a genuinely durable finish and understandably not one most people are willing to consider today. Oil finishes are what make the same result available now: a floor that resists foot traffic and moisture, lasts decades, and stands as a real alternative to wood, concrete, or tile.

The oil is not protecting the floor. It is making it.

This is the thing that separates an earthen floor from every other surface we finish, and it explains everything else in this article.

On wood, the substrate is already strong. Take the finish away and you still have a floor, just a vulnerable one. What you have after an earthen floor is poured, dried, and burnished is compacted clay, sand, and fiber. Beautiful, and about as durable as a hard dirt road.

The oil is the difference between simply dried earth and a floor. It soaks into the clay matrix, fills the spaces between particles, and polymerizes into a solid network locked through the surface. After that the floor sheds water, takes daily wear, and mops clean.

Why linseed and tung

They are hardening oils, and that is not negotiable here.

A hardening oil polymerizes: it reacts with oxygen and cures into a solid. A non-polymerizing oil never does. It stays soft, stays sticky, and eventually goes rancid in the floor. You cannot substitute one for the other and get a floor, no matter how food safe or natural the alternative sounds.

For earthen floors we recommend our Earth Finish, a blend of high quality linseed and tung oils, citrus oil, beeswax, and pine rosin. Once those oils fully polymerize the surface is highly resistant to water and daily wear. Water beads on it, and the floor can be mopped without concern.

Before you start: the floor must be completely dry

This is the single most important precondition and the one people rush.

Any moisture still in the floor when the oil goes on gets trapped there, and unlike wood, an earthen floor has no way to release it later. That becomes a problem you cannot fix from the surface.

If you are unsure, wait longer. Nothing about this job rewards hurrying, and this step least of all.

Applying the finish

Mask first. Painters plastic and tape on any adjacent surface you want to protect.

Go barefoot, or wear old socks you are willing to throw away. No shoes on the floor during this process.

Start in the corner furthest from the entrance and work toward your exit.

Do the edges first, and get ahead. Brush 3 to 4 coats around the entire perimeter before you move into the main field. Edges and field absorb differently, and getting the perimeter built up first is what keeps them matching.

Then the field. A lambswool applicator pad or a roller works well for pushing oil around. A sprayer also works.

The first coat can go on heavily and should absorb readily.

Second coat timing depends on the room. In a large room you can return to your starting point and begin again immediately. In a small one, wait until most of the first coat has absorbed.

Repeat to four coats, or to the point where the floor will not take any more.

You will know when the floor is full, because significant puddling starts. Wipe the excess up with a dry, clean rag.

Do not panic at the mottled look. A freshly oiled floor looks patchy and uneven. That evens out as the oil keeps absorbing, and the color settles.

Curing, and how to know when it is ready

Stay off the floor for a week after the final coat. Not light traffic, not socks. Off.

Then test it. Take the edge of a trowel or a putty knife and try to indent the surface, pressing hard. If you feel any movement under the edge, any give or sliding, the oil needs more time. If it is hard and dry, the floor is ready for use.

That test is better than any number, because curing depends on temperature, humidity, and airflow. Warm, dry, moving air gets you there fastest.

The oils keep hardening well beyond that point, and the floor keeps getting tougher for months. Be careful with heavy furniture and point loads early on.

Going further: sanding, buffing, and wax

Once the initial finish has hardened, you have options.

The floor can be sanded or buffed for a smoother surface.

Our Liquid Wax End Sealer can go on as a top coat for a higher surface sheen. Wax also has a practical advantage over the years: you can re-wax a heavy traffic area on its own and it blends, without redoing the whole floor.

Living with an earthen floor

Do not mop a new floor for at least a week after completion.

Shoes off is worth adopting as a house rule.

Sweep and vacuum regularly, damp mop occasionally. When mopping, use only diluted oil based soaps. Linseed floor soaps and Murphy's Oil Soap both work. They clean while adding oil back rather than stripping it.

Never use solvents on an earthen floor. Not citrus, not pine, not alcohol, not ammonia, not chlorine. Anything that dissolves oil dissolves what is holding your floor together. On wood a bad cleaner damages a finish. Here it attacks the structure.

Protect against point loads. Floor protectors under chair and table feet, a hard mat under rolling chairs, carpet or thick cardboard laid down when moving anything heavy. Never drag furniture.

Clean up spills promptly, pet accidents included.

Re-oil or re-wax every five to ten years, depending on traffic and how often the floor has been mopped with oil soap.

Cleanup

Pure Citrus Solvent for spills, overspray, and brushes. Turpentine or mineral spirits also work.

Where to learn the rest

Pouring, drying, and burnishing an earthen floor is a craft in its own right, and this article assumes you have already got that far. For the construction side, we recommend Earthen Floors: A Modern Approach to an Ancient Practice by Sukita Reay Crimmel and James Thomson, now in its second edition. They describe the process and the materials thoroughly and well, also include chapters on finishing your floor and it is the book we point people to before they pour anything.

Earthen floors reward hands-on training. If you are considering doing one yourself, take a workshop before you take on a room.

 

• Questions about how much your floor will take, or about bringing an older earthen floor back? Call us at 541-844-8748 or write info@heritagenaturalfinishes.com.

 

• This article grew out of an earlier version written by Ziggy Liolia, who also took the photograph, and reflects methods developed alongside Sukita Crimmel of Claylin, with whom we have worked closely for many years.