Date: September 10, 2021
“Who would have thought that sandbags could be inspirational? They were originally used for flood control and military bunkers but they have now been adapted for home construction. The bags are made of natural materials like hemp or burlap or more durable synthetic materials like polypropylene which is water, rot and insect resistant. These bags are filled with 70% sand and 30% clay and are laid in courses to build the walls, similar to bricklaying. The most common structures look like big beehives or igloos as the curved walls provide good lateral stability. The system has no tensile strength, so the structures must be built into compression forms like domes and arches. However, they could take on other forms like straight walls if they are topped with conventional roofs.
The earliest version of earthbag homes can be traced to Gernot Minke, a German professor. However, it gained momentum thanks to Nader Khalili, an Iranian architect. He established the California Institute of Earth Art and Architecture in Hesperia. Khalili developed and patented the superadobe building system, which uses mile-long fabric tubes that can be pumped full of soil and laid in coils to create a structure. He envisioned these structures providing temporary housing in case of natural emergencies or for low-cost housing. His most popular design is the Eco Dome, 400 sq ft structure that was featured on HGTV.
Both earth and the polypropylene or burlap bags are cheap. Also, you don’t need a large, experienced crew on site which cuts down on construction and contracting costs. Other than the bags and the barbed wire that holds the bags together, earthbag building is a natural building that doesn’t use any other resources like wood or metal. As for structural integrity, these houses seem to withstand seismic, wind and snow loads. They apparently also survive fires, floods and hurricanes. Also, if the house is properly plastered, it will keep out mold, insects, and rodents. Thermal mass is another.
Earthbag domes are the most structurally sound but it’s difficult to use space efficiently when the walls are curved. All your furniture and finishes have to be custom made. Size is another concern. The maximum recommended diameter of earthbag homes is 20 feet or 6 meters, however, you can connect these homes together or build underground to increase the building’s footprint. If you are taking out a loan, there’s a strong chance you won’t be approved for this kind of building with no precedent in the area, because you the lender can’t estimate your home’s value. Tied to this is the unpredictable resale value of the home. On the structural side, you must be careful not to use biodegradable material like leaves when you are filling the bags with earth, because this will disintegrate and leave gaps in your walls causing them to become unstable. If the sand to clay ratio on your site isn’t ideal, which it probably won’t, you will have to truck in mounds of dirt to your site. In Texas for example, where I live, the soil has a very high percentage of clay. Earthbag homes are also very labor intensive. Finally, the scalability of this model and how much of an impact this construction is really going to make. It is a potential solution for disaster shelters but it is difficult to mass produce these homes.”