The number one barrier to home ownership is affordability. Many people can’t afford a home made with expensive modern materials, and bank financing. That’s why earthbag building, and natural building in general, is becoming so popular. Why not build it yourself – in stages if you have to – with low cost materials and pay with cash as you go?
Let’s look at the materials required to build a small $300 earthbag dome at about $6/square foot. (Detailed building instructions at Instructables.com)
– Recycled or misprinted bags: Polypropylene bags are widely used for rice, sugar, fertilizer, animal feed and other uses. You can often find used bags at low cost, or you can order misprinted bags at reduced cost from a manufacturer. The standard size for earthbag building is 18”x30”. Mesh bags and burlap bags are others option if you can get them cheaply.
– Subsoil: This is usually available at or near the construction site. Some builders dig a pond and use the excavated soil to build their home. Excavating companies frequently have excess ‘fill dirt’ they’ll gladly sell for cheap, especially if they’re working in the area and you can reduce their trucking costs. Excessively clayey soils can be mixed with sand from a stream or river bed (often available free for the hauling). Overly sandy soils can be mixed with a bit of clayey soil to make more solid earthbags. Another source is sand and gravel producers, who often have ‘reject fines’ or ‘road base’ at low cost.
– Gravel: This is a good fill material for lower courses and can serve as a low-cost ‘gravel bag foundation’. Gravel and/or rubble from old driveways or sidewalks can be broken up and used in a rubble trench under the first course of bags.
– Barbed wire: This adds a lot of tensile strength, which is critical for domes. Most builders use new barbed wire between courses since it’s not a major expense for a small structure. But for those on a tight budget, using recycled barbed wire from old fences is another way to save money. (Make sure it’s in good condition, especially for domes.)
– Tamped earth floors and earth plaster: Experiment with your local soil and find a mix that is suitable. If it shrinks and cracks excessively, add sand. If it doesn’t adhere well, add clay. Adding chopped straw or other fibers will reduce cracking. Earth plaster can become a work of art, with almost any color imaginable. Your floor could be made simply by tamping the mineral subsoil that’s under the dome, although in most climates it’s advantageous to add insulation under the earth floor (such as scoria or pumice) and a moisture barrier.
– Doors, windows and vents: These can all be salvaged. Short pieces of pipe can be buried in the wall for ventilation. Insert some screened pipes low in the wall and some up high on different sides of the building for optimum ventilation. Some builders add operable skylights for greater ventilation and lighting. Arched window and door openings can be formed from barrels, tires or forms built of wood scraps. Consider using old wagon wheels or culvert pipe for window frames.
– Exterior plaster or living roof: Unless you’re living in an extremely dry desert, you’ll need to protect your structure from moisture damage. There are numerous options. Some builders used a soil cement mix to create a reptilian-like scaled surface. Most use lime or cement plaster. Another way is to put 6 mil plastic sheeting and earth over the dome and create a living roof with plants. Living roofs are very beautiful, but they do require a lot of time and effort, and a favorable climate.
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