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Volunteers building an earthbag houseBuilding with Earthbags - Nature's Cheapest and Most Plentiful Building Material
by Staff Writer

Earthbag construction has been around for at least a century, but it is gaining in popularity as modern and innovative designs are developed. Although earth is one of the oldest building materials known to man, state and county building codes are just starting to evolve to include contingencies for alternative and green building methods and materials. Earthbag architecture has also been suggested as a method of providing a quick but durable shelter in emergency situations. Sandbags are still used by the military to protect against bullets, bombs, and shrapnel, so it should provide more protection than a traditional stick-built house.

Although it sounds very simple, there is some science and strategy that should be considered when planning your earthbag structure. Not all filler material is created equally -- the denser the material is, the less insulation value it will offer. Volcanic rock, pumice, and rice hulls are commonly used materials that offer high insulation values, but heavy clay soil and sand can still be used. This is especially true if insulation value isn’t the highest priority. In areas where water may collect, a rubble trench should be used as a foundation to prevent moisture from wicking up into your walls. In colder climates, the foundation needs to be of an appropriate depth to prevent problems caused by heaving.

In an effort to maximize the green potential of the building project, many builders choose to use misprinted polypropylene bags when available. The reject bags are usually a reasonable value, and they're put to a good use instead of heading to a landfill.

Bags are filled and compressed with a metal tamper or with flat boards and body weight as the structure’s walls get higher and higher. Between each course, the bags are held in place by two strips of four-prong barbed wire. This helps keep the bags from sliding or settling as the weight from additional courses pushes down on them.

Windows and door openings can be created by forming arches or by using a lintel to bridge the opening. The options are almost endless when it comes to roofing; a traditional roof can be built and anchored to the walls, or a complete dome can be formed using only bags. If a second floor is desired, one technique is to pour a reinforced concrete bond on top of the first floor's walls. This bond secures the bags and evenly distributes the weight of a roof or second story.

As the wall construction is completed, the walls need to be protected from the elements. UV rays from the sun will quickly weaken polypropylene, hemp, and burlap bags alike. The walls also need to be kept as dry as possible to keep bugs, mold, and mildew out of your structure. Natural earth plasters or modern cement stucco will provide a durable, long-lasting finish to your cheap, sturdy earthbag structure.

If you have built with earthbags, we would like to hear from you and share your story on this site. Please contact webmaster@ this site if you are interested.