Quick Answer
When building an earthbag foundation, consider the site's drainage, soil stability, and structural integrity. Earthbags are placed in a specific pattern to provide stability and distribution of weight. The foundation must also be designed to accommodate the intended structure's loads.
Site Preparation and Drainage
Earthbag foundations require a well-draining site to prevent water accumulation and erosion. Ensure the area slopes away from the structure to prevent water runoff. A minimum slope of 1% to 2% is recommended to facilitate water drainage. The site should be compacted to a depth of 12 inches (300 mm) to a stable base material, such as gravel or compacted soil.
Earthbag Construction Techniques
To build a stable earthbag foundation, use polypropylene bags filled with soil or a combination of soil and aggregate. The bags should be stacked in a running bond pattern, with each layer offset 6 inches (150 mm) from the layer below. Barbed wire is often used to tie the bags together, providing additional stability. For dome-style structures, use a spiral pattern to create a curved surface. For straight walls, use a rectangular pattern with a slight angle to prevent water from running down the wall.
Plastering and Finishing
Once the earthbag foundation is complete, it can be plastered with a mixture of soil, sand, and cement to create a durable and weather-resistant surface. The plaster should be applied in multiple thin layers, allowing each layer to dry before applying the next. This process can take several weeks to complete, depending on the thickness of the plaster and environmental conditions. A smooth, even finish can be achieved using a combination of hand tools and mechanical sanders.
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