Any building material can have one or more of several characteristics:
Is it indigenous (common) to the area?
Does it provide thermal mass for insulation and heat conduction?
Is it durable or susceptible to rot?
Is it easy to work with or does it need specialized training to manipulate?
Most typical modern building materials will only satisfy one and perhaps two of those characteristics. There is not a single modern material used that satisfies all four characteristics. However, the materials used to produce the building blocks for the Earthship’s primary structure encompass all 4 aspects of the best building material: used tires.
All around the world we have materials used for construction, but not all materials are available everywhere. Shipping materials over long distances requires enormous amounts of energy. This is not sustainable. In order for everyone to have access to housing, the buildings need to use materials that can be found all over the world, while still being able to maintain a low energy impact on the planet. One answer is the construction material found in every Earthship: used tires. In any country in the world there is a glut of used automobile tires, usually clogging up landfills or the ocean. In Earthships, these tires form the basis of the foundation.
To use these tires requires little to no energy, because it is already in a form ready to use. All building materials used for Earthship structures use little to no energy to manufacture into use. This allows Earthships to be easily accessible to everyone. Even a large scale production would still have a low impact against the planet.
Dense materials must be used in the walls surrounding the Earthship. This dense material allows the Earthship to store temperatures required for a habitable environment. An Earthship is similar to a rechargeable battery, except the “energy” stored is actually temperature.
For all of human history, societies have created structures out of wood. However, because it is an organic material, it is biodegradable and therefore can deteriorate. This, along with wood having a high absorbency level, creates a poor quality building material.
However, wood is a good material for products such as cabinets or interior uses where the mass is not an issue and is protected from elements that can cause rot. When creating a building, the exposed structure should be made of a natural resource, one that is massive and durable in its own right. Tires are extremely durable, able to shed off water and able to last centuries.
Natural phenomenom are one of the biggest threats to structures. Heavy rains, earthquakes, natural deterioration (rot) are three phenomena that can impact most homes. If foundations are built with wood or concrete, they are susceptible to fracturing or breaking in the face of these events.
One of the fundamental elements for affordable and sustainable housing is it must be easy for everyone to understand how to construct the dwelling. The skills required are basic, and it must be easy to learn and master all in a short amount of time.
Having a specific talent such as construction or engineering is not important to build with used tires because skills and instructions are created in basic forms. This allows everyone the opportunity to master the needed skills and techniques.