A fairly recent idea in green building is the earth bag technique. As the name implies, this novel approach uses bags filled with earth to build structures. The bags are stacked just like bricks, except that instead of using mortar, barbed wire is placed between courses to hold the bags in position. These walls are over a foot thick and have excellent thermal mass. They have the added benefit of being easy to work with, as long as you can fill a bag with 50 to 75 pounds of dirt, and lift it into place.
You can use any type of dirt if your bags are durable enough, but for best results you should use a mixture of about 30% clay to 70% sand. For added durability, you may add a little lime or cement to each bag. Alternately you can pound each bag with a sledgehammer. Pounded earth solidifies like concrete. Just be careful not to pound a hole in the bag!
A trick commonly used in order to save money when building this way is to obtain misprinted polystyrene feedbags from your local feed and seed store. These bags are the ideal size, shape and material for this building method. Once the bags are filled, they can be covered with a stucco plaster just like adobe. If you plan to plaster your walls, you might want to incorporate chicken wire into the walls to help the plaster adhere better.
When using this style, windows and doors are framed up separately, and then simply inserted into the walls when the proper level is reached. The remaining bags are stacked on top of them until the roofline height is attained. An additional benefit to using this method is that you don’t have to frame up a separate roof. With a little skill and practice, you can make a dome roof by starting with a circular wall and gradually decreasing the size of the courses until they meet overhead.
When building with earth bags, long walls (over 20 feet in length) will have to be buttressed for support. The best way around this is to simply avoid building walls over 20 feet in length. The smaller the structure, the less energy is required to heat and cool it.
As with most earth-friendly building styles, you will have to work closely with your local building inspector to make sure you are meeting code requirements. If you’re planning to build a house this way, you should probably practice a little first by building a tool shed or a workshop. Once you’ve built up your skills and confidence, you can tackle a larger structure. Since there is no mortar in this method, you can always take the bags apart and restack them if you make a mistake.
Does this sound like the building method for you? If so, you may learn more at Caico’s Dream at: http://www.caicosdream.com/build/ebag.html.
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