Floor Finishings - Part One

August 2025: Work Week

Once the interior walls and ceilings had been fully covered with lime wash, we were ready to turn our attention to the bare concrete floors, poured back in summer 2023. 

We talked about a lot of different ways to finish and seal the floors. I loved the idea of doing concrete epoxy for a highly stylized and modern effect, but after watching many videos online of DIYers attempting this finish on their own with mostly disastrous results and costly mistakes, we scaled back our ambitions. And we didn’t have the budget to hire someone to do this treatment for us.

Instead, we opted to try a leather-floor effect that Dash had read about in the book How to Build an Underground House by Malcolm Wells. Mix 1 part wood stain with 3 parts polyurethane on a sealed concrete floor. Sounds simple enough, right? The product will create dark and light lines and “wrinkles” in the natural grain of the concrete to appear like aged leather.

We chose a colour (Burnt Sienna by Minwax), a concrete sealer (Behr low-luster) and a floor polyurethane (Behr floor finish).

We decided to apply with a roller instead of an air sprayer since we did not have an air sprayer on hand and it is another tool that often requires lots of practice to master proper application. Then I did some elaborate math and I got to work. (Brice worked on cleaning the lime wash off all the bottle walls during this time.)

I chose the bathroom floor to begin as a kind of experiment space, knowing there would be a shower/tub covering a lot of that floor area later.

The first order of business was to clean the lime wash droplets off the concrete floors. I was expecting this floor finish to be fairly light in opacity and that the droplets would show through if they weren’t cleaned up. This required the labour-intensive and dusty work of manually scrubbing the concrete with a wire brush to lift off dried lime wash, then sweeping and vacuuming up the dust for a clean floor. 

Later, we also tried a belt sander on the floors in the kitchen U to try and speed up the cleaning process. This proved to be too strong of a tool to control and for the task at hand. It created a verifiable indoor dust storm and more concrete was coming off the floor than desired. Back to the manual wire brush!

The concrete sealer was applied after cleaning. I left some lime wash droplets as a test to see how well it would be covered up by the stain/polyurethane treatment.

Then the stain/polyurethane mix was applied in the 1:3 ratio. It was a much more opaque result than what I was expecting. No leather look appearing here! I couldn't tell you why. We had no hints from the Wells book.

Nice colour; very opaque; not what I thought would happen.

I decided to leave the bathroom floor with this single application for the time being. The U room floors were a higher priority and the bathroom could be revisited later. The work week was almost up as well. I managed to clean and seal the kitchen U before leaving the project until the next visit.

Sealer applied.

September 2025: Extended Work Weekend

Upon returning to the Earthship for an extended work weekend, I decided to experiment further with the floor finish recipe in the kitchen U room. Start light with less stain in the mix and go from there.

The first application was the “lightest” opacity at ¼ cup of stain to 3L polyurethane.

I didn’t like the end result. It looked sloppy when it was wet and when it dried.

I could see how the effect was supposed to come through the concrete grain, but I realized applying with a roller was going to be an issue. Too many lines were being created from the roller. An air sprayer would be necessary for this opacity recipe to create a seamless application. The colour was also giving more basketball than Burnt Sienna. It was a bit disappointing. Time to add more stain!

In the end, I went with the ¼ cup of stain to 1L polyurethane as the final recipe and it took 4 applications to achieve a consistent, final look that I was happy with. The concrete sealer was yet to be done to complete the floor treatment.

At this point, while the kitchen floor was curing, the living room/bedroom U had been occupied by the solar battery system while Dash had been working on things in the utility room, including building a custom cabinet off-site to store the batteries permanently.

The cabinet was ready to be installed during this weekend. We got that custom cabinet carefully crafted by Dash inside the ‘ship in order to move forward on the floors as well as reconnect the solar power system. (Thank you, Dash!) Brice and Dash heaved those heavy 100lbs batteries into place.

After the usual wire brush scrubbing and vacuuming, I applied 3 coats of the stain/polyurethane mix before running out of time for the weekend and the end of the season. It pained me to walk away from an unfinished project, so close to being done. But it had to wait now until 2026!

Earthship Tour Video 2025

 View a short video of what the Earthship looked like near the end of the 2025 build season.