Rammed earth outdoor shower

After the hand-thrown walls, earth plasters, and soil-cement floors it was finally time to get going with rammed earth. We thought a few low walls for an outdoor shower would be a good place to start. Six feet high, eight inches thick and no roof load, but exposed to all the Hana rain and to the shower water would be a good introduction to how well rammed earth could work in this climate. The backside of the wall serves as a landscape wall for the front door to the main pavilion.

We poured concrete footings and then set short section wall forms much like we did years ago on the mainland. We only had a small 13 cfm air compressor that would barely power a Jet 2-T rammer, so most of the wall was rammed by hand. Evan and Dan helped with the first corner, then Cindy's brother Alan and his kids came for a week to help on the shower wall and to plant bamboo. Khyber and Taj were here as well, so it was a family wall raising. It only took a few days.

We were trying to arrive at a good mix design for rammed earth that wouldn't require import from the other side of the island. The soil on site has no plasticity, being all volcanic in origin and not old in geologic terms, but it is expansive and will crack if not modified with aggregate. We added about 40% coarse red cinders that are available here in Hana and 7% Hawaiian cement. Getting the correct water content was also tricky. We had a tendency to overwater the mix and then ramming was a little spongy. We only had four wall sections total, but felt pretty good about how things turned out in the end.

The walls have now been exposed to seventy inches of annual rainfall for eight years and the surfaces are as durable as the day we stripped the forms. Mosses and lichens have colonized the face; blue ginger and yellow alamanda grow against them. Ferns grow in the joint between the base of the wall and the shower floor.

The shower walls gave us all the confidence we needed to move into the first of the rammed earth pavilions, which I'll describe in upcoming posts.

Finishing the first pavilion

We worked quickly to finish the main pavilion, at least to a point where we could move in and quit paying nightly rentals. As I remember, it was about six weeks from the day the containers were off-loaded to the day we moved in with doors and windows, a working stove, frig, shower, toilet, and water heater. We had help from nieces, nephews, friends, children, and friends of children. It was like a barn raising island style. We had fish most nights and made it to the beach every day after work.

The main elements of this first building were: slab on grade foundation and floor, steel pipe roof framing with corrugated metal roof cover, hand-thrown earth walls, large sliding doors so the walls would open up, and a few interior partitions of earth plaster on foam cores. We had cut all the pieces for cabinets and wooden doors and loaded them in the container before we left, so assembly was fast on site. All the furniture and appliances were in the containers, along with dishes, bedding, towels and clothes. This was the challenge I'd set: to pack the containers with all the building materials, plumbing and electrical rough and finish, plus furnishings we'd need to build a house and be able to call it a home in a short period of time. Although we found a lot of room for improvement, I think we proved the concept - that a shipping container can be loaded in such a way that, with a few skills, the things in it can be turned into healthy shelter.

I've put together a few photos for this post showing the first pavilion finished. There were other components of the construction I haven't covered yet, such as the soil-cement floors and the pre-cast earth pavers, but that is because I think they are better illustrated with photos taken during work on the other buildings. In the next couple of posts I want to talk about the outdoor spaces and how getting started on the landscaping was just as big a part of moving onto the land as was the building.

In the photos you can see the way building one looked by itself, plus a shot of the bathroom with Kusumi's lime and earth plaster and the kitchen with his cement and earth plaster.

Earth plaster with Akira Kusumi

One spring in the late 1990's, we were invited to Japan to conduct a workshop in rammed earth. At the workshop we met Japan's most renowned and respected plasterer, Akira Kusumi. Among his other work, Kusumi is responsible for the periodic re-plastering of the Imperial Temple. All traditional plaster in Japan is clay-based. We became friends at the workshop, traveled to Kyoto for another visit together, and then I invited Kusumi to Napa to conduct a plaster training for our crew.

When it came time to develop the earth plaster formulas for the Shipwreck experimental station, we of course asked Kusumi to come and help us. Not only did he bring his expertise, but two boxes of Japanese plastering tools as gifts. We had three different soils, a black, brown, and red: a yellow sand, a gray sand, Hawaiian cement, and hydrated lime. Kusimi was looking for the right combination of gritty and sticky. He'd try a certain proportion of soil and sand and test it on his hawk for texture until it had the feel he wanted.

He actually used several different formulas throughout the house. For base coats on the interior walls he'd use copious amounts of long-chopped straw, and low-cement contents. For finish coats we used less straw, chopped finer, and lime rather than cement. Lime gives you more time to work the plaster smooth. Cement plaster is harder and more resistant, but also more difficult to work, especially for amateurs, which we certainly were. For the entry he used traditional Japanese plaster - pure earth and chopped straw with no cement or lime. With no stabilizer, you can come back the following day and steel trowel a final finish, tightening the surface and working out the small shrinkage checking.

Kusumi and Masako were here for a week. We worked pretty much all the time, and finished all the interior partition walls as well as finish coats over the hand-thrown walls in the bathroom and the kitchen. Kusimi's mastery of his craft was remarkable to observe. He could cover a wall in one-tenth the time it took either me or Khyber, and where our work ended up full of trowel marks and cat faces, his was smooth and flat. I have all of the formulas recorded in the formula log. Let me know if you're interested.