It used to be more common to find buildings made from earth (think of adobe houses in the southwest). We’ve stepped away from that over time, relying on other resources like metal and wood.
In an attempt to return to local materials and long-term sustainability, we’ve been experimenting with rammed earth.
I first became interested in rammed earth construction back when I heard about it in a college class. And when I started working in the central valley, I saw the rich soil and wanted to try it out. We experimented with a couple prototypes, collecting soil from various locations to see which samples had the right amount of sand and organic material. It turned out that the native soil worked the best.
To make the rammed earth bench, we took the earth, added 5% cement and compressed everything in layers. The soil in Escalon is a light gray color, so we added some stucco pigmentation to get varying colors — orange, brown, red — to imitate the soil samples we collected in the Sierra foothills.
We started by adding 7 inches of moist soil, and compressed it in a wooden mold to a 4 inch layer. The pressure creates a tight matrix of soil and sand that bonds with the cement, forming a solid, durable brick.
We made a fun weekend of it, bringing a team of volunteers out from San Francisco to participate. The end result is beautiful, and it’s made from 95% organic material from the site.