Not very much information on this subject is available and little has been written in the way of building with Earthbags. But this eco-friendly building method has been in practice for hundreds of years. You probably drive by an Earthbag structure everyday. Many highway embankments and overpasses are built using Earthbags as is retaining and retention walls. Sandbags, Earthbags and geotextiles-call them what you will-are a great eco-alternative to concrete.
You can fill an Earthbag with just about any material, allowing you to easily excavate a building site and use the materials leftover to fill the Earthbags. Rock, gravel, sand-even lava rocks work perfect for filling up Earthbags. Whatever fits into the basic 24″ wide poly bags.
Castles made of sand melt into the sea, eventually. That’s why Earthbag structures must be built with plenty of drainage in mind. Installing a French Drainage Trench is the first step for proper drainage. The footer of the wall is also the French drain.
A good two feet or more of material behind the Earthbag wall must be excavated in order for proper drainage to take place. A 6mil construction grade vapor barrier provides a water barrier. Once the Earthbag wall is constructed, it is then backfilled with drainage gravel.
As Earthbags are filled and stacked in alternating layers, each layer is then secured to the next. Four-point barbwire is laid in two rows down each course of Earthbag. This grabs each bag and holds it in place with little penetration to the bags itself.
Stack Earthbags so that each one staggers back from the last, making the walls tilt outward towards the surrounding soil. This allows for compression of the wall and prevents it from toppling over from the weight of the exterior soil.
As gravel is backfilled into the cavity behind the Earthbag wall, it should be mechanically compressed every 24″ to provide additional support and drainage.
In especially moist or damp soils, drainage is a must. An additional section of silt fence (geotextiles) should be placed against the exterior of the Earthbag wall to prevent exterior moisture. Place a layer of silt fence, then a few courses of Earthbag wall. Lift the silt fence up and over the Earthbags and work your way to the top.
Once the Earthbag wall is stable and has settled over at least 28 days, you can then finish the interior of the wall however you like. Plaster, stucco and even cobb will easily adhere to the rough surface of the Earthbags, creating a smooth, finished wall.