Sharing information and promoting earthbag building
|Do-It-Yourself Earthbag Building
by Dr. Owen Geiger
By now you've probably heard of earthbag building and are looking for more detailed information. This article summarizes how you can build safe, beautiful and durable homes, offices and shops out of earthbags (sandbags) for very little money.
For those of you new to earthbag building, here's a quick overview. Earthbag building has evolved from the military's use of building with sandbags to build blast and bullet proof structures. Sandbags also have a long history of use for flood control, which demonstrates their incredible strength, moisture resistance and ease of use by novices. A big reason for the growing popularity of earthbag building is its low cost. You can build small domes for $100-$1,000. For $1,000-$5,000 you could have a nice, small home that would likely outlast most conventional wood-framed houses, and be quieter and more comfortable.
The building process itself is as simple as filling bags with soil, gravel or insulation, stacking in level courses and tamping them solid. Barbed wire is placed between courses for added strength and to prevent slippage. Earthbags excel at providing dirt-cheap housing in harsh climates and areas prone to disasters such as hurricanes and floods. It's easy to create curved walls, domes, roundhouses and other shapes for above grade or below grade structures such as rootcellars and storm shelters. The building techniques are very easy to learn and very few tools are required.
Things you will need: shovel, bucket, garden hose, wheelbarrow, gravel, soil, earthbags (sandbags), barbed wire, wire cutters, level. Most earthbag projects use 18" wide x 30" long bags when measured empty. Misprinted bags and recycled bags from farmers and feed stores are often available at reduced prices. In addition, you'll need a tamper to compact the bags and a slider to help place bags on top of barbed wire. Tampers are sold at large building supply centers, or you can make one yourself using the free plans on our website. A slider looks similar to a cookie sheet, but with a larger grip on one end. It can be made from scrap metal, such as old furnace heating ducts.
1. The first step is to prepare the building site. You want a level space clear of roots, rocks and other obstacles, and with enough space to work and pile materials. Remove and store topsoil for landscaping. Mark where the building will go with temporary stakes and then stockpile mounds of gravel and earth (and insulation if you're building in extremely cold climates). Distribute the piles evenly to minimize labor. Now you're ready to stake out the building with batter boards as conventionally done by carpenters. Check for plumb, square and level. For domes, put in a center stake and trace a circle in the earth using a length of twine. Locate where the plumbing will go and bury all plumbing lines before proceeding.
2. The easiest, least expensive foundation is a rubble trench. Expensive reinforced concrete foundations aren't needed. You can save thousands of dollars on this step alone. Dig a trench slightly wider than the earthbag wall. Dig the trench about 18"-24" deep and add gravel, rocks or broken concrete to about 6" of grade. You want at least one course of bags below grade. In wet climates, it's best to add a French drain to remove excess water.
3. Once the rubble trench is leveled, you're ready to place the first course of bags. It's recommended to double-bag the first few courses of gravel for added strength and peace of mind. Gravel prevents moisture from wicking up into upper courses. In cold climates you can use lava rock or pumice to create an insulated foundation. Fill the bags about ¾ full and fold the end underneath. If money is really tight, you can stitch the ends closed and save on bags. A 'bucket chute' (plastic bucket with the bottom cut out) helps holds the bag open and makes it easier to fill. Tamp the bags flat after each row is complete. Add one or two strands of 4-point barbed wire between each course. Two strands are recommended for domes. Bricks or rocks are helpful for keeping the wire in place. Use the slider starting on the second course. The slider allows you to position the bag above the barbed wire. When the bag is aligned, hold it in place and pull the slider out with a quick motion. Add courses until you're at least 6" above the risk of moisture getting in the walls. Domes require two stakes and stringlines. The center stake is used to verify roundness. The second stake defines the dome curvature. For domes, each course of bags is corbelled - they overhang the previous course slightly. It is best to keep earthbag walls protected from sunlight with tarps until plastered.
4. Set the door form(s) in place. Plumb and level the form(s), and brace in position. Forms for doors and windows can be built with scrap wood from pallets, or you can use barrels, tires, culvert pipe, wagon wheels, etc.
5. Now you're ready to start building walls with soil-filled bags. You can also build walls with bags of scoria, pumice, perlite, vermiculite or rice hulls. This creates an insulated wall with bags that are light and easy to work with. Most subsoils are adequate and can be obtained from the site. Or you can have road base, reject fines or fill dirt delivered by the truckload and save hundreds of hours of hard labor. You can add sand or clay to modify the mixture. The best mix is about 25% clayey soil and 75% sandy soil. Stack the bags end to end with the folded end against the previous bag to prevent spillage. Tamp solid once each course is complete. Check each course for level. Adding the same quantity to each bag (example: 4 buckets of soil) helps maintain level. Repeat the above process for each course.
6. Set window forms in position, and continue stacking and tamping bags.
7. For domes, you can continue the same process of corbelling each course. Near the top corbels may get larger, depending on the desired shape. For vertical walls, it's easiest to build a bond beam immediately above windows and doors. This saves building lintels. Reinforced concrete or wood bond beams are both acceptable.
8. Build the roof if you're going with vertical walls. Create large overhangs of approximately 36" to protect walls from moisture damage.
9. At this point you can plaster the walls. In most cases plaster mesh isn't required. For disaster prone areas, mesh is recommended. For high risk areas like earthquake zones, add mesh on both sides of walls and tie together. Plastic mesh may be preferred because it won't rust. Fishnet is a low cost substitute, but not as strong. Also for high risk areas, you can add poly strapping that runs under the bottom course and up and over the bond beam (cinch together with a strapping tool). Earth plaster is recommended for interior walls and exterior walls protected by roofs. Domes require a more durable plaster, either stabilized earth or lime. Additionally, you can create a green roof by covering the dome with two layers of 6 mil poly and then adding earth and plants.
Owen Geiger, Director of the Geiger Research Institute of Sustainable Building has teamed up with Kelly Hart to create this website to better focus and keep track of the rapid growth of this novel building method. Geiger's new site at earthbagplans profiles 75 small, affordable earthbag house plans.
Article Source: EzineArticles.com
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