How to build a rammed earth house
(Page 2 of 3)
September/October 1973
By John O. McMeekin
I didn't finish the foundation before I started to ram the walls of our house because [1] the walls were less expensive to work on and [2] doing only one thing gets monotonous. If you involve yourself in a project like this, vary your self-assigned tasks ... you'll both get more done and limit your chances of becoming bored with the whole project.
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WALLS
You'll need a new set of forms when you begin to ram the dirt walls. On the advice of South Dakota State College Bulletin 277, Rammed Earth Walls For Farm Buildings (which I obtained from the college at Brookings, South Dakota, although—I'm afraid-the pamphlet is long out of print), I built my first framing from 2 X 12 planking. The planks, however, turned out to be too heavy for one man to handle, and my wife was about to have a baby ... so I followed the bulletin's diagram (Fig. 2) but made new forms from 5/8" marine plywood.
The wooden molds—which were lined with shoot steel and edged with 3/4" angle iron—clamped onto the foundation and were reinforced with 4 X 4 uprights. These boxes were light enough for one man to move and their metal lining was a considerable improvement because it left the sections of wall smooth. You'll need three pieces of 4 X 8 plywood to make one of the L-shaped forms shown in Fig. 2. The outside section measures 8' X 4' and the inside 7' X 3'. The mold should be one foot wide.
Next you'll need a tamper (mine weighed about 15 pounds and had a six-foot handle of one-inch pipe threaded into it). Then the work begins: Shovel a four-inch layer of dirt into the form and pound the earth until it rings like rock. Then add four more inches ... and so on. Cover your forms at night to protect the soil from rain, and keep precipitation from the walls as you go.
Since rammed earth hardens as it dries, the forms may be removed as soon as they're full. Pull out the bolts that hold the form in place and fill the holes which are left. This is easily done by bending a piece of tin into a "V", holding the guide against one of the openings in the wall, filling the chute with dirt and pushing the soil into the hole with a bolt.
Stagger the joints on your second course. The easiest way to do this is to place a dummy, one-foot-long, unthreaded bolt crossways in the compacted dirt about 18 inches from the end of the first form. When the frame is pounded full, remove the dummy and you'll have a hole in which to insert the first bolt for your next, form (thereby giving you an 18" shorter-than-ordinary section). As you move along, frame the window openings with 2 X 12 planks ... and again, brace them!
Embed a 14" anchor bolt with a 3" washer about every three feet along the top course of earth. These bolts will hold the cap ... a 2 X 12 plank which will serve as a footing for your roof. By the way, how will you know when any two walls are exactly the same height? Easy! Tape a glass tube to each end of a garden hose, and string this gauge from one wall to the other. When the hose is filled with water and the liquid's level matches the top of both partitions, you're all right.
