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 the earth fill and does not have access to air.

Tire walls provide massive thermal storage — each tire contains roughly 100 to 150 kilograms of earth with a high specific heat capacity. A south-facing tire wall with south-facing glazing in front of it functions as a giant thermal battery: absorbing solar energy during the day and releasing it as heat during the night. This passive solar performance is the most important functional characteristic of the tire wall system.

From a structural standpoint, tire walls have been demonstrated to perform well in seismic zones. The rubber of the tires provides a degree of flexibility that rigid masonry lacks, and the massive weight of the walls provides seismic inertia. Pangea has developed building codes and structural calculations for tire wall construction that have been used to obtain permits in multiple jurisdictions.

Tire Wall by the Numbers

• A pounded tire weighs 135–180 kg (300–400 lbs)

• A standard Earthship tire wall is 3 tires (courses) high = approximately 66 cm (26 in) thick

• Thermal mass per running meter of wall: approximately 2,000–4,000 kg

• Compressive strength: sufficient for two-story construction

• Fire resistance: very high (sealed rubber, no air access)

• Seismic performance: excellent (flexible rubber, massive inertia)