The tire wall is the primary structural system of the Earthship model and the most widely used natural building system in Pangea’s work. It is elegant in its simplicity: recycled automobile tires, which would otherwise end up in landfills or tire fires, are filled with compacted earth and stacked in a running bond pattern (like bricks) to form the building’s primary bearing walls. The process of filling a tire, called pounding, involves placing the tire on a rubber mat, shoveling earth into it, and then using a sledgehammer to compact the earth until the tire is completely full and has bulged out at the sides into a slightly trapezoidal shape. A fully pounded tire typically weighs between 135 and 180 kilograms (300 to 400 pounds) and, once stacked in a wall, is virtually indestructible. The resulting wall is also inherently fire-resistant, since the rubber of the tire is sealed within…