How to Build Your Own Dirt House
Building with dirt to make your own house can significantly reduce the need to transport materials to remote locations, which will often cut costs. This is why significant portions of the Great Wall of China used rammed earth construction. This method is more environmentally friendly, reducing transportation costs of materials and your carbon footprint. Additionally, rammed earth can be used in areas where materials are difficult to come by but labor is more available. This method of building is beautiful and creates walls that resemble marble but have a high mass like stone.
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Things You'll Need
- Foundation (pre-poured)
- Two plywood boards
- Skill saw
- Tape measure
- Three 8-foot long 2-by-4 boards for the wall form
- Two sheets of plywood for the wall form
- Three more 8-foot long 2-by-4 boards for the corner form
- Two sheets of plywood for the corner form
- Six 3-foot steel I-bar clamps
- 6-foot pipe with a 6-inch square of 3/4-inch thick piece of steel
- Soil
- Concrete (10 percent of wall's overall mass)
- Penetrating concrete sealant and waterproofer to coat the wall
- Suitable roof with wide, overhanging brim
Instructions
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Prepare the foundation so that it can handle the walls with the same specifications that would be required by your building codes as if you were building the walls out of 2-foot thick stone to the height that you are planning. Use reinforced concrete that is poured below the frost line, is 1 foot above the ground and (if needed based on the weakness of the soil) 3 feet wider than the wall.
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Build the forms for the walls. To build the forms, cut a plywood board the long way down the center to make two long boards that are 2 feet wide and 8 feet long.
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Make a frame to support the outer edge of this wall form. Along one side where the edge of the plywood is 8 feet long, screw an 8-foot long 2-by-4. Attach the board to the plywood, on the thin edge of the 2-by-4 board. Screw another 8-foot long 2-by-4 board along the other edge of the plywood.
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4
Cut a 2-by-4 board into four sections that are each 21 inches long. On the 2-foot wide sheet of plywood, arrange the four sections like ladder rungs between two 8-foot long 2-by-4 boards. Screw these boards to the plywood with the 1 1/2-inch edges facing the plywood. Do the same thing to the other plywood board.
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5
Take apart the steel I-bar clamp by sliding off the end of the clamp. Drill holes with a hole saw bit that are big enough to thread the 3-foot adjustable steel I-bar clamp from one side of the form to the other. Slide the end of the clamp back on. Position the clamp on the edges of the last two 21-inch boards that were screwed onto the plywood. Set the four clamps to a 2-foot depth.
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Cut a 2-foot wide strip of plywood that is 8 feet long. Screw a 4-by-4 that is 8 feet long on the center of the 2-foot wide strip so that the 8-foot lengths are oriented the same direction. Use two clamps along the edge of the form to hold this 2-foot wide strip with the 4-by-4 on the side facing the interior of the form. Make another one of these ends on the other (open) edge of the form.
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Place the form over the foundation and clamp the form. Set all of the clamps to a 2-foot depth. Weld a 6-foot (or longer) pipe to the middle of a flat sheet that is 6 inches square.
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Add water to the soil. You want to add the minimum amount of water so that the sand sticks together like it would if you were making a sand castle. Most recipes use 9 parts of this soil mixture (above) and one part concrete (made the traditional way before being added) to stabilize the walls that are being built. Pour dirt suitable for the wall into the form, about 6 inches deep at a time.
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Use the flat sheet welded to the pipe to tamp down (pound) the dirt by grasping the pipe and then slamming it down onto the dirt, repeatedly. Tamp the dirt very well to compact it into artificial "stone." It will have properties similar to sandstone.
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Unhook the clamps and slide them out of the form. Slide the form up the wall. Align the holes at the bottom of the form with the holes in the top pf the wall. Reinsert the claps to hold the form at the same 2-foot depth as before and then add the next layer. Continue this process from the foundation floor to the ceiling height to make each wall.
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Slide the form to the side of the first wall, removing the end that is now replaced by the wall that you have just made. The groove in the previous wall created by the 4-by-4 board will hold up the new wall as an interlocking joint. Check to see that the walls are bound to each other well while your work progresses.
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Corners should be supported by a corner form that is made in the same way as the wall form but with the outer wall of the form extending 2 feet past the inner wall of the form, toward the corner. Do this with another form touching this new form to form the corner. Add hinges to the corners where the boards meet to keep the forms together for use at the next corner.
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Seal the wall with a penetrating sealant to make the wall water resistant. Ensure that there is adequate drainage at the wall and that the roof is built so that it keeps the walls dry.
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Tips & Warnings
Some builders recommend encasing the entire wall to avoid the time-consuming efforts of removing and re-positioning the forms. Before you start, send in samples of the soil that you intend to use for qualitative analysis to a local university's geology department. The qualities to test for include compressive and tensile strength, permeability, abrasive qualities, cohesion, plasticity, stability, erosion resistance, shrinkage and swelling (see Resources for more information). According to the Food and Agriculture Organization of the United Nations, the ideal soil mixture is as follows: The dirt mixture should be anywhere from 5 to 20 percent clay and 10 to 30 percent silt (both being a combined total of 15 to 35 percent of the overall material). The sand should be from 35 to 80 percent of the mixture, while the gravel should be 0 to 30 percent of the mixture, to make the combined total of the sand and gravel components a total of 50 to 80 percent of the total mixture. Cobble is considered suitable if it is less than 10 percent of the overall mixture. The organic matter should be less than 3 percent of the total mixture. Soluble salts need to be less than 1 percent of the total mixture. Do not allow the wall to stay in prolonged contact with water and ensure that it is not infiltrated with water. Protect the wall from erosion and ensure that the water drains away from the wall.
Hire a general contractor with experience in rammed earth walls and ensure that he follows all laws (local, state and federal). Consult an engineer at every step of the process, and heed her advice. Rammed earth often ends up costing more than traditional methods if done carefully and quickly. Make sure that you can get insurance for your building. Tips for negotiating insurance for your home are given in the Resources section.
