Rammed Earth Homebuilding

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Twenty years and 500,000 cubic yards of moist soil later, I'm still asking myself the same question: why isn't rammed earth in more widespread use? Without doubt it is a lot of work, as are most things of value in life, but the beautiful simplicity of converting raw, natural earth into human habitat involves a sort of sweaty alchemy. If you attempt to build your own rammed earth house, and if the process works as well for you as it has for me, you'll never regret the effort.

Earth is poured into wooden forms, simple structures which can be as large or small as you wish. Here, the builder has chosen to use large forms covering the whole perimeter.

Planning Your Home

Design criteria for an integrated project must grow out of the site. It goes without saying that architecture should be responsive to the climate of its region—the Cape Cod saltbox and the Texas dog run evolved to suit very different sets of climatic conditions—but working with specific site conditions is equally important to successful design. Where does the sunlight enter the house? When and from where do the winter storms come and the prevailing breezes blow? Does the topography or a great view dictate a preferred spot for the garden, the kitchen, or the living room? How about privacy, road noise, or potential future development? These factors and many others come into play during the development of a site-appropriate design.

The moistened earth can be rammed inside the formwork either quitly with hand tampers, or, as shown here, with pneumatic backfill tampers hosed to air compressors.

You've no doubt asked yourself a few questions already about a home made of soil. "What happens when it rains? ";"How do they stand up over time?"; "How much do they cost?"; and "How good are their insulating properties?" I've wished countless times that I could have had a large sign hovering over me which simply read, "Nothing, well, nothing, not much, and terrific:"

Predictably, the answer to each of these questions is far more involved than that simple statement would indicate. The resistance of the walls to rainfall is a factor of the soil type, the rate of stabilization, the degree of compaction, the amount of protection afforded the wall, the drainage at the base, and the climate. Durability (including earthquake resistance) is dependent upon the strength of the wall, the design of the building, the quality of construction, and the force of the earthquake. The cost of a rammed earth house is affected by the design of the building, the slope and accessibility of the site, the percentage of owner-supplied labor, and the degree of finish work.

Finally, the R-value question is even more complex. Dense materials such as adobe, concrete, stone, brick, and rammed earth have R-values roughly equivalent to .25 per inch. In other words, an 18-inchthick earthwall would appear to have a total R-value of only 4.5—far from adequate to meet today's strict performance standards, even in mild climates, where R-11 is the minimum wall insulation. If this is true, how can it be that an adobe house feels "warm in winter and cool in summer;" as it is so often reported?

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