One of the primal attractions to building with earth is harvesting raw materials from the construction site itself. In the old days (pre-industrial revolution), that was always the case. Soil dug from the foundation trenches or from a nearby borrow pit was either molded into sun dried bricks and laid up into block walls or rammed between wooden form boards into monolithic walls. Man converting raw local resources into shelter is truly sustainable building.
During the past decade or two, the earthbuilding industry has drifted away from this core precept, settling into the comfort zone that comes from using familiar and consistent quarry-processed aggregates. This quest for comfort has come at an environmental cost.
Don’t get me wrong, I am all in favor of consistency and dependable results, but I’ve also become more aware of the carbon consequence of putting trucks on the road, burning diesel fuel, wearing out rubber, and pounding asphalt. I trucked quarry materials to our rammed earth and pise jobsites for years, but I now believe the right path is to improve our understanding of local geology and our skills at formulating mix designs to allow us to incorporate even more of each site’s unique resources.
I think of it as the construction industry’s version of the slow food and locavore movements - better quality, closer to home. I want to call it “building from the watershed”. The goal is to develop a series of protocols that allow us to evaluate any found soil and predict how it will perform in a structural capacity. When we complete the assembly of this soils library, we will then have the ability to reproduce consistent results from site to site, using fewer quarry amendments and thereby reducing the number of trucks on the road and CO2 in the atmosphere. Carbon offset construction.