The tire-soil wall was based on the "Earthship" concept of construction made popular by Dennis Weaver. While such walls are often arched and built into hillsides, our prototype Earthship wall required end supports made from recycled lumber to be free-standing and meet the six-foot length constraint. The end supports do not significantly contribute to the structural strength of the wall.

Discarded Celotex insulation was used in the bottom of each tire to provide a means of containing the soil in the tire. We found that this insulation was not only quite easy to break when compacting the soil, but also caused an allergic reaction in one of the students. Although using the Celotex provided a way to recycle waste, we would not use it again for this application.

The Earthship took four hours to assemble to the state shown in the previous image. On the second day of lab, extra clay remaining from the construction of the other walls, along with extra glass bottles, were used to fill in the spaces between tires. The resulting wall is extremely strong, and has significant thermal mass.

While the Earthship wall may not be as aesthetically pleasing as the Mortar-Bottle wall, it has promising structural strength and thermal properties. Any number of exterior and interior finishes could be applied to render the aesthetics of the wall to meet design requirements. We were surprised to find that it really does take three wheelbarrow-loads of soil to fill one tire completely, but our learning curve for efficiently compacting soil within the tire geometry was steep. We also learned that tires are not all the same size, requiring creativity and pre-sorting to create a consistent and stable wall.