Designing Rammed Earth Tire Walls

Earthship construction pioneered the reuse of discarded automobile tires as structural building blocks. Each tire is packed tightly with soil to create a heavy, stable module that functions much like a large adobe brick. Building a wall from these tires requires estimating how many units will be needed, how much soil must be shoveled and compacted, and the overall mass of the finished wall. This calculator assists planners by turning a few dimensions into those quantities so they can schedule labor, source fill material, and ensure the foundation can support the load.

Tires come in many sizes, but most Earthship designs favor passenger car tires with outside diameters around 0.75 meters and sidewall heights of roughly 0.25 meters. When the tire is laid flat and rammed with earth, the sidewall height becomes the vertical thickness of one course. The outside diameter governs how many tires will fit along the wall length. By dividing the target wall length by the tire diameter and the wall height by the tire height we can estimate the number of tires required in each course and the total number of courses. The product of those two numbers gives the total tire count. The simple relationship is expressed below.

In the equation, N is the number of tires, L is wall length, D is tire diameter, H is wall height, and h is tire height. The ceiling function accounts for the fact that fractional tires cannot be used; any remainder requires an additional full tire. When planning a curved wall, the length parameter should follow the centerline of the curve. Because tires interlock, a rule of thumb is to add an extra tire per course for overlaps at the ends. The calculator presents the exact integer counts and leaves users to adjust for special shapes.

Determining the volume of soil needed involves approximating the shape of the rammed tire. A perfect torus would be difficult to model, so builders often approximate each packed tire as a solid cylinder with diameter equal to the tire's outer diameter and height equal to the sidewall height. The volume of one tire of this form is given by the classic cylinder formula shown below. Multiplying that volume by the total tire count yields the volume of soil to be collected or delivered.

The weight of the wall is then simply the volume multiplied by the density of the soil used to ram the tires. Most designs assume a moist, well compacted soil with density around 2000 kg/m³. If the soil contains more gravel or is particularly dry the density may be slightly lower. The calculator allows this value to be adjusted. Accurate mass estimates help engineers verify that foundations or supporting berms can carry the load. Rammed earth tires are extremely heavy, often exceeding 130 kg each, so care must be taken when stacking them to maintain worker safety.

To illustrate how these relationships play out, the table below lists tire counts and soil volumes for a sample wall using common dimensions. The values assume perfectly straight walls, but they provide a sense of scale. Even a modest ten meter long wall three meters high requires more than one hundred tires and over ten cubic meters of packed earth. Planning for such quantities ahead of time avoids project delays and ensures enough volunteers or machinery are on site for the build.

Earthship walls deliver several environmental benefits. They divert large numbers of tires from landfills, each of which encapsulates a significant volume of soil. The thermal mass of the packed earth moderates indoor temperatures by absorbing heat during the day and releasing it at night. Because the tire sidewalls are shielded from ultraviolet light and oxygen they degrade very slowly, extending their usefulness for decades. Proper drainage and waterproofing prevent water from accumulating in the tires, which could otherwise attract mosquitoes or freeze in cold climates.

Construction proceeds by laying the first course of tires on a leveled foundation, packing them with moist soil using sledgehammers, and checking for level. Each subsequent course is staggered like masonry to distribute loads and provide interlock. As courses rise, rebar or pins can be driven through sidewalls to tie tires together, and voids are filled with smaller earthbags or mortar. The calculator's output gives builders a realistic idea of how many work sessions will be needed and how much earth must be staged nearby. Many crews find that a single tire takes fifteen to thirty minutes to fill depending on soil moisture and team experience, so multiplying the tire count by that time yields a labor estimate.

While the tool uses simple geometric models, users should remember that actual tires have hollow centers which are partially filled with soil. The approximation of a solid cylinder slightly overstates volume, but the extra margin is often desirable. Designers may also adjust tire dimensions if they source light truck tires or mix sizes. Uniform sizing simplifies stacking, so it is common to select a single tire model and collect enough units from recycling yards or garages before beginning construction. The calculator aids by showing how many of that chosen size must be gathered.

The completed wall can be finished with plaster, earthen renders, or even left exposed in utilitarian structures. In climates with high moisture, a breathable lime plaster protects the tire sidewalls while allowing vapor to diffuse. Some builders add insulation on the exterior or interior depending on heating and cooling strategies. Because rammed tire walls are non combustable and extremely massive, they offer excellent fire resistance and sound attenuation. These qualities, combined with the embodied recycling, make Earthship style walls attractive for sustainable housing, retaining walls, and bermed greenhouses.

Using the Earthship Tire Wall Material Calculator provides a starting point, but on site adjustments are inevitable. Window and door openings reduce the number of tires and can be framed with wooden bucks inserted into the courses. Corners may require half tires or specially cut units. Nonetheless, the ability to quickly estimate materials with a simple formula enhances project planning and helps communicate the scope of the build to collaborators, permitting authorities, and community members.

Ultimately, the calculator underscores the practical logistics behind the romantic image of off grid living. Filling hundreds of tires demands stamina and coordination. The wall's tremendous mass necessitates thoughtful drainage and structural support. By crunching the numbers before breaking ground, designers can stage resources efficiently and avoid surprises. The web tool encapsulates best practices from the Earthship community in a concise interface that encourages experimentation with dimensions and materials.

Whether you are planning a full Earthship home, a retaining wall for a terraced garden, or an experiment in sustainable construction, knowing the quantity of tires and soil involved is essential. This calculator blends geometry with practical experience to deliver those insights instantly. Adjust the defaults, explore the impact of alternative tire sizes, and use the results as a foundation for detailed construction drawings and schedules.