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Compressed Earth Blocks ... Cheaper Than Dirt!

Updated on June 13, 2014

Turn dirt into stone-like bricks that last centuries!

Compressed Earth Block (CEB), is mechanically-compressed soil, formed into a brick or block. CEB are made from clay-based dirt (subsoil), an aggregate such as sand, and a small amount of stabilizer such as lime or cement. CEB blocks are utilized in constructing homes and businesses across the world, and are the "greenest of the green" in building technology. CEBs are installed onto the wall by hand and typically use a bonding slurry made of a soupy version of the same dirt/clay mix, sans aggregate. CEBs which use lime as a stabilizer undergo a chemical change to become ever harder and more stone-like the more they age and are exposed to moisture...they literally become rock, lasting for centuries!

Housing Projects for the Mortenson Center in Engineering for Developing Communities, CU-Boulder
Housing Projects for the Mortenson Center in Engineering for Developing Communities, CU-Boulder

Compressed Earth Blocks

Sustainable Green Building (no Green Thumb required)

The advance of CEB into the construction industry has been driven by manufacturers of the mechanical presses, a small group of eco-friendly contractors and by cultural acceptance of the medium in areas where it is seen as superior to adobe. In the United States, most general contractors building with CEB are in the Southwestern states: New Mexico, Colorado, Arizona, California, and to a lesser extent in Texas. However, manufacturers of the mechanical presses enjoy their heaviest sales overseas. Mexico and Third World countries have been attractive markets for the presses for years.

The advantages of CEB are in the wait time for material, the elimination of shipping cost, the low moisture content, and the uniformity of the block thereby minimizing, if not eliminating the use of mortar and decreasing both the labor and materials costs.

CEB can be pressed from humid earth. Because it is not wet, the drying time is much shorter. Some soil conditions permit the blocks to go straight from the press onto the wall. A single mechanical press can produce from 800 to over 5,000 blocks per day, enough to build a 1,200 square feet (110 m2) house in one day. The Liberator, a high performance, open source CEB press, can produce from 8,000 to over 17,000 blocks per day.

Shipping cost: Suitable soils are often available at or near the construction site. Adobe and CEB are of similar weight, but distance from a source supply gives CEB an advantage. Also, CEB can be made available in places where adobe manufacturing operations are non-existent.

Uniformity: CEB can be manufactured to a predictable size and has true flat sides and 90-degree angle edges. This makes design and costing easier. This also provides the contractor the option of making the exteriors look like conventional stucco houses.

CEB had very limited use prior to the 1980s. It was known in the 1950s in South America, where the Cinva Ram was developed by Raul Ramirez in the Inter-American Housing Center (CINVA) in Bogota, Colombia. The Cinva Ram is a lever-action, manual press that makes one block at a time.

U.S. manufacturers produce much larger machines that run with diesel or gasoline engines and hydraulic presses that receive the soil/aggregate mixture through a hopper. This is fed into a chamber to create a block that is then ejected onto a conveyor.

During the 1980s, soil-pressing technology became widespread. France, England, Germany and Switzerland began to write standards. The Peace Corps, USAID, Habitat for Humanity and other programs began to implement it into housing projects.

Construction method is simple. Less skilled labor is required; wall construction can be done with unskilled labor encouraging self-sufficiency and community involvement. If the blocks are stabilized with cement and/or fly ash, they can be used as bricks and assembled using standard masonry techniques of brick-laying.

Soil mix conditions: The soil mix is 15-40 percent non-expansive clay, 25-40 percent silt powder, and sharp sand to small gravel content of 40-70 percent. The more modern machines do not require aggregate (rock) to make a strong soil block for most applications. Soil moisture content ranges from 4 to 12 percent by weight. Clay with a plasticity index (PI) of up to 25 or 30 would be acceptable for most applications. The PI of the mixed soil (clay, silt and sand/gravel combined) should not exceed 12 to 15; that is the difference between the Upper and Lower Atterberg limits, as determined by laboratory testing.

Foundations: Standards for foundations are similar to those for brick walls. A CEB wall is heavy. Footings must be at least 10 inches thick, with a minimum width that is 33 percent greater than the wall width. If a stem wall is used, it shall extend to an elevation not less than eight inches (203 mm) above the exterior finish grade. Rubble-filled foundation trench designs with a reinforced concrete grade beam above are allowed to support CEB construction.

Advantage Goes to CEB - What could possibly be greener than dirt?

  • Non-toxic: materials are completely natural and do not out-gas toxic chemicals
  • Disaster Resistant: Fire can't burn the wall, tornadoes will have a tougher time huffing and puffing to blow the walls down, and earthquakes can't shake the solid construction. Walls are completed with a steel-reinforced concrete bond beam to keep the house solidly sturdy for centuries.
  • Sound Resistant: Noisy neighbors? No problem. Thick walls insulate you from unwanted outside noise.
  • A Healthy Home: CEB homes are naturally mold resistant because there is no cellulose material – such as in wood, Oriented Strand Board or drywall – that can host mold. Those who suffer from allergies will find refuge in a clean allergy-free CEB home.
  • Century siding: the best finish is a lime plaster stucco. Lime has the eco-advantage of low embodied energy in production, plus the durability of lime stucco can last beyond a lifetime. Lime stucco allows the home to "breathe" moisture, causing a natural afternoon cooling effect, and an evening warming effect on the interior of the home. CEBs that are stabilized with lime or some cement can be left exposed with no outer plaster.

The CEB Story - To Build a Village - Open Source Ecology

Get the Dirt on Building Codes!

Who knew dirt could be so strong?

CEB’s strongest market in the USA is probably New Mexico, which has incorporated the method into its Earthbuilding Code family. The first CEB Code Development meeting in New Mexico took place Dec. 12, 2001. The persons present at that meeting are considered today the leading experts in the field. They include:

Fermin Aragon, general bureau chief of the Construction Industries Division for Santa Fe, New Mexico

Joe M. Tibbets, publisher of Adobe Builder Trade Publications, Bosque, New Mexico

Larry Elkins, Adobe International Inc., Milan, New Mexico

Jim Hallock, Earth Block Inc., Pagosa Springs, Colo.

Lawrence Jetter, A.E.C.T., San Antonio, Texas

Jim Hands, P.E., Red Mountain Engineering, Santa Fe, New Mexico

Todd Swanson, Bio-Hab Inc., Hesperus, Colo.

Joaquim Karcher, architect, Taos, New Mexico

Code work was completed June 10, 2002 and melded into New Mexico’s new section, R1100 Earthen Building Materials.

The CEB code is different from the adobe code in numerous respects. For instance, the CEB code allows slip mortars and permits blocks ejected from a press to go directly to the wall.

CEB Strength: Using the ASTM D1633-00 stabilization standard, a pressed and cured block must be submerged in water for four hours. It is then pulled from the water and immediately subjected to a compression test. The blocks must score at least a 300 pound-force per square inch (p.s.i) (2 MPa) minimum. This is a higher standard than for adobe, which must score an average of at least 300 p.s.i. (2 MPa)

It must be emphasized that the compressive strength minimums for code compliance are nothing like the true strength of CEB blocks. New Mexico only sought to assure that CEB would be at least as strong as adobe.

CEB can have a compressive strength as high as 2,000 pounds per square inch (13.7Ã106 Pa). Blocks with compressive strengths of 1,200 (8.27Ã106 Pa) to 1,400 p.s.i. (9.65Ã106 Pa) are common.

Thermal advantages: Also, due to the enormous mass – these are monolithic walls – CEB has excellent thermal performance, reducing heating and cooling costs.

Thermal testing: From May 31 to June 3, 2004, the Biology Dept. of Southwest Texas Junior College, Del Rio, Texas, conducted tests for thermal change on three structures: concrete block, adobe and compressed earth block.

Results indicate the interior temperature of the adobe and CEB modules were significantly lower than for concrete blocks.

With a maximum ambient temperature of 107 °F (42 °C), the interior temperatures were:

Concrete Module: 111 °F (44 °C) (four degrees Fahrenheit above ambient)

Adobe Module: 95 °F (35 °C)

CEB Module: 91 °F (33 °C)

The CEB module was consistently cooler inside than the adobe by approximately 3 degrees.

Use Thermal Mass to Your Advantage!

Thermal advantages: Also, due to the enormous mass - these are monolithic walls - CEB has excellent thermal performance, reducing heating and cooling costs.

Video You Can Dig Into! - Sometimes you just gotta get dirty

Feedback on CEBs! - Let me know what you think

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