More Resources

Books

Adobe and Rammed Earth Buildings: Design and Construction by Paul Graham McHenry

The Rammed Earth House: Revised Edition by David Easton

Earthbag Building: The Tools, Tricks and Techniques by Kaki Hunter and Donald Kiffmeyer

Earth-Sheltered Houses by Rob Roy

The Fifty Dollar and Up Underground House Book by Mike Oehler

Water Storage: Tanks, Cisterns, Aquifers, and Ponds for Domestic Supply, Fire and Emergency Use by Art Ludwig

Rainwater Harvesting for Drylands : Guiding Principles to Welcome Rain into Your Life And Landscape by Brad Lancaster

Websites

What is Rammed Earth Construction
USC School of architecture

Rammed Earth Q & A
Greenhomebuilding.com

About Adobe
El Paso Solar Energy Association

Building with Earthbags
Overview of Natural Building Techniques
Natural Paints
NetworkEarth.org

EarthArchitecture.org

Southwest Solar Adobe School

Adobebuilder.com

Adobe House Plans
Adobebuilder.com

Sustainable Building and Living

Primitive Semi-Permanent Homes
Survival and Self-Reliance

Green Building Resources
EPA.gov

Sustainable Sources

Habitat for Humanity

Natural Building Network

Green Building Basics

EarthHandsandHouses.org

Sustainable Energy

Otherpower.com

Alternative energy info
Energy Savings Trust, UK.

Alternative Energy Institute

Country Skills and Native Arts

Continued from Page 3

Housing Construction

A lean-to shelter or bark tee-pee will keep you safe in a survival situation, but after the doomsday dust clears, you'll want to build a solid, comfortable dwelling for the long haul. While European settlers wasted no time felling the forests to erect their first homesteads, a log cabin may not be viable in an era of global warming. Mega-wildfires and continued clear-cutting have pretty much diminished this natural resource in any event.

firebudd.com

Scientists worldwide are predicting the possibility of gamma ray bursts, massive solar flares and a weakening magnetic field, suggesting that any new home must block ultraviolet rays and other incoming radiation. And more forceful storms, including tornadoes and hurricanes, suggest that builders need to rethink their construction materials long before any doomsday scenario unfolds.

One way to prepare for the worst-case scenario is to go underground. Alternatively, uou may decide to build into the side of a mountain, like the Native Americans did at Mesa Verde. See Evacuation Strategies for more on the bunker angle. Another option is to build thick walls with adobe or rammed earth. Not only have people used these plentiful materials since remote antiquity, but most dwellings can be equipped to survive tornadoes, ultraviolet radiation and a nuclear blast.

Working with Adobe

In the desert southwest, Native Americans were first on the scene to develop an easy-to-use, long-lasting building material by mixing equal parts sand, silt and clay, then adding straw and water to create adobe. The mixture is poured into wooden (or cardboard) forms to make adobe bricks, typically 14 inches long, 10 inches wide and 4 inches thick. To produce one or two dozen bricks at a time, the forms are laid out on a flat expanse of ground covered with sand to prevent sticking. Likewise, the wood/cardboard is oiled to prevent the adobe from sticking to it.

A tool called a screed is used to flatten the poured mixture and scrape it level across the top of each form during the pour. After the bricks dry in the Sun, the forms can be lifted and moved to a second location (if necessary)for the next pour. Several hours to a day later (depending on the temperature), the finished bricks can be picked up and stacked on edge for use in a few weeks.

digistuff.com

When it's time to build a house or other structure, a string is laid out and tied to a stick from point to measured point to insure the walls are built straight across, as well as plumb (upwardly straight). Then starting from each corner, the walls go up, with each layer of bricks offset by four inches or so, as shown in the photo. A brick can be scored with a sharp edge and then cut in half (or another size) so that it will fit where a whole brick won't.

A mortar to hold all the bricks together is made from adobe mud containing no rocks or straw. Ideally, you'll spread a three-quarter-inch thickness of this mud evenly between each layer and each brick. The trick is to build straight, level layers with no cracks or crevices, or porosity in the mortar itself.

As the walls go up, window and door openings have to be factored into the equation. Typically, builders use plywood, two-by-fours, or wooden boxes, inserting them as the walls go up to preserve the space needed. Since the top part of a door or window frame will hold up a significant load, you may need to extend the length of the wood beam so that it can carry the weight. Considerations like these must all be worked out before the walls are laid.

Either during the wall construction or within a few days afterward, passageways for pipes, wiring or vents must be dug out of the adobe. Otherwise the bricks will harden and become nearly impenetrable.

David C. Peterson Construction

After the brick layers are in place, it's customary to apply several inches of adobe mud coating to both the interior and exterior of the brick walls. Use a trowel to spread the mud across, two inches at a time. When the first coat is dry enough, you can start the second.

Floors can be made from adobe mud, but moisture rising up from the earth can in some cases be even more of a danger here than with the walls or roof. Lime may be incorporated into the formulation.

Adobe roofs should be installed after the walls and adobe floor are finished. Roofs are traditionally flat in the southwest (due to the lack of heavy snowfall), with wooden logs spaced across the four adobe walls to provide structural stability. The space between the logs is filled with adobe. However, given the fire danger and shortage of wood, alternative solutions may have to be incorporated. In general, you'll need some form of a frame to hold the adobe and/or other fill-in materials. It's also essential to waterproof your rooftop and have it securely attached to the walls in order for it to survive strong winds. In earthquake country, the corners of your structure should be reinforced for seismic strentgh. Use steel rebar, if you have it, and be careful to drill tight holes in the brick to accommodate its diameter. (You can squeeze a little mortar around the rebar after the bricks are laid.)

Santa Fe MLS

Testing your adobe recipe: Depending on the geology of the area, your adobe formula may have to be tweaked in order to get just the right combination of ingredients. Clay content is especially important, because if it's not plenty elastic and flexible, or if the amount of water added is off, the adobe will crack and shrink, or slump to one side (from too much moisture). Straw can also wick moisture from the outside into an adobe wall, which is not a good thing. If too much water seeps in over time, the adobe will sag beneath the weight of the higher, dryer part of the wall and eventually fail. However, adobe's ability to breathe is one of its best advantages, and it should never be sealed with any plastic or petroleum-based product.

Before the brick-making operation goes into full swing, builders carry out a set of tests to make their recipe is spot-on. A few bricks are formed and allowed to dry, then broken open after one and two weeks, and a month. Each brick is first inspected for shrinkage and cracks, then for tensile strength by dropping it to the ground from six feet high. You can also test its strength by piling on 150 pounds of weight to see how it reacts. (Generally, a brick should handle 300 psi worth of pressure.) One other test involves the brick's reaction to getting wet. While adobe is supposed to be breathable, you don't want to see water channeling its way through it.

Other adobe tips:

Working with Rammed Earth

Rammed earth is a construction method with an impressive resume. It was used for long sections of the Great Wall of China, as the core foundation of ancient pyramids, and in the erection of many European castles. Today's version of it incorporates some of the same techniques and specifications described in the adobe section above. A typical rammed earth formulation relies on two-thirds sand and a one-third silt/clay combination. As in the case of adobe, the properties of the clay of the clay plays a critical role in assuring long-lasting strength and durability of the mixture. It needs to be sticky and elastic, without much shrinkage or cracking after it cures.

Terra Firma Rammed Earth Builders

Rammed earth requires a slightly more labor-intensive approach to mixing it together, especially if stabilizers like Portland cement are added to the formula. Rototillers or cement mixers are used by builders to make sure all the ingredients combine well. Even before the recipe is mixed, a garden sprinkler may be brought into action overnight to slowly dampen the earth pile. In particular, this moisture activates bacteria in the clay but there should be no excess of it. The standard recipe calls for 8 percent water, 92 percent dry material.

Rammed earth construction also differs from adobe in that there's no brick-making. Instead, the walls are poured exactly where they will stand. Large, heavy forms generally stretch the length of the wall, accommodating a two foot high section of wall for each pour. The moist (but not wet) earth is dumped into the long form, then "tamped" down to compress it as compactly as possible. There's no straw in the recipe, so this denser dirt pack is expected to hold together by sheer force. Modern builders will usually add some gypsum or Portland cement as a stabilizer to hedge their beds, and include steel rebar in the same manner as a concrete pour.


Rammed earth construction site in Tibet. Notice the tampers on top of the forms and porters carrying up the earth. Photos: Christine Louise Rutherford

After the first two-foot high wall is set, builders have the option of installing a similar section on each side of the house, or completing the first side entirely before moving around the corner. Load-bearing walls generally run 18 to 24 inches thick. Non-load-bearing walls may be 10-14 inches thick.

As in the case of adobe, window and door openings, as well as any passageways or shelves have to be cut out or otherwise accounted for at the time the walls are laid.

Testing your rammed earth recipe: Before you break any ground on the property, you'll have to test the soil to see if it's the right stuff to work with. To do this, put some earth into a jar (excluding topsoi), then fill the jar with water and shake it up. The sand should settle on the bottom (after a few hours), while the clay and silt will rise to the top. If sand doesn't make up two thirds of the mass, then you may have to tweak your formula.

The second step is to determine if the the clay makes up about half the clay/silt combination. Clay also needs to be plastic enough to hold your rammed earth mixture together, especially since you're not using straw or any other fiber. If for some reason the earth on your property contains less than optimal proportions, you can sniff around elsewhere for clay, silt and sand, then manually combine your own blend of the three component, plus any additives.

As with adobe, you'll want to form some test blocks of rammed earth and break them open after one, two and four weeks to see how they look.

Once you start mixing your final product, you'll also want to perform a moisture test. One way to do this is to take a handful of the mixture and rub it into a dirt ball. The ball should stretch and hold together when manipulated in your hands, but when you drop it to the ground, it should crumple back into loose earth. If it doesn't crumple, the mixture is too wet to pour and tamp. If it breaks apart in your hands, it may be too dry. If the test fails no matter how much moisture is used, either your proportions are off or the clay needs to be checked.

groundhouse.com

Before You Build

Should you decide to construct a home or other structure in advance of a doomsday scenario playing out, keep in mind that nearly all municipalities and townships in the United States enforce strict building codes. Normally, you're required to get a permit prior to breaking ground, submit architectural plans (i.e technical drawings) and invite building inspectors to your location to make sure the codes have been implemented correctly. In California and other seismically active areas of the country, additional code requirements are enforced, including the need to bolt your home to a foundation and reinforce each corner of the building (on each floor).

While there are numerous how-to books on the subject, housing construction is fairly complicated, so consider volunteering on a friend's new home or local community project to learn the ropes. Habitat for Humanity and similar organizations sometimes recruit unskilled volunteers for their programs in New Orleans and elsewhere. In addition, many community colleges offer low-cost training in both commercial and residential construction, although they generally focus on modern methods, like concrete foundations, wood-framing, PVC pipe installation and sheetrocked homes.

A number of sustainable and green building organizations have sprung up in recent years, offering advice, resources and training in alternative construction techniques. You can get all the latest news from their websites. Check the gray box on the right for listings.

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