Compressed Earth Block Questions and Answers

For those interested in learning more about compressed earth blocks (CEBs) this is an excellent informational site of Instituto Tierra y Cal,  a non-profit organization that envisions a global resurgence of healthful and sustainable rural communities.. Below is a summary and frequently asked questions. CEBs are environmentally friendly, soundproof and bug proof.

“CEB construction is an earth-friendly building technology that is superior to concrete and wood construction in terms of its health benefits, affordability, durability, and energy efficiency.  CEB technology is a contemporary improvement of ancient earth building methods.  Stabilized CEBs are made of clay, sand and a small percentage of lime and/or cement that is compressed by machine.  The benefits of CEB, especially in low-income and marginalized communities, are many.  Suitable soil is abundant and blocks can be compressed using manually operated or powered presses at a low cost.  The health, comfort and durability of CEB buildings are superior to that of concrete block or fired brick constructed structures, the predominant building materials and methods in rural areas of the global south.  Because of their thermal mass, CEB homes naturally provide some passive heating and cooling, providing increased comfort for it’s inhabitants.  This appropriate technology is also environmentally friendly and transferable to large and small-scale applications.  Reliance on forest resources is largely eliminated and energy consumption in the production of blocks is many times less than that required for fired brick and concrete.”

Earth block FAQ

Q: What are Compressed Earth Blocks?
A: Soil! Or rather, soil which has some clay content, ideally, 12% – 25% clay. Soil with higher clay content can be mixed with sand or sandier soil to get a successful mix. The soil is frequently obtained from the ground at the building site. Roughly 65% of the soil on the planet can be used to make CEBs – and it can be found in many locations.

Q: How are Compressed Earth Blocks made?
A: Production of CEBs can be achieved manually or mechanized. The basic procedure is:
The soil (the “qualified” soil with some clay content) is broken up and larger granules of soil, sand and gravel are removed by sifting through 1/4″ to 3/8″ inch wire screen.This dry, screened soil and sand ( if necessary) are then mixed well, adding 4% – 10% lime and/or cement to the mix if you are making stabilized blocks (CSEB). The mixing can be done by hand with shovels and rakes or by larger machinery, adding just enough moisture to the mix to achieve a 10% – 12% moisture content. The soil is compressed and molded into uniform blocks in a hand-operated press or a mechanized hydraulic press, stacked, covered and cured for 1 month.

Q: What is the difference between stabilized and unstabilized earth blocks?
A: A CEB is stabilized by adding a small amount of lime and/or cement to the soil with some clay content. The lime, with the small amount of moisture, chemically combines with the clay, essentially turning back into limestone, locking in the sand and gravel to form a CSEB which is water resistant. CSEBs are more expensive than CEBs because of the cost of the stabilizer. Unstablized CEBs are typically protected by roof overhangs and by coating the outside of the structure with a lime plaster.

Q: Why would you want to build with Earth Blocks rather than concrete?

A: First: COST. CEBs are significantly less expensive than concrete because the materials are locally available (thus eliminating or greatly reducing both material and transportation costs). It is cheaper to stabilize CEBs with a small amount of lime and/or cement or to protect unstabilized CEBs with lime and/or clay plasters than to build with concrete blocks or wood.

Q: Are there other advantages to Earth Block homes?
A: A CEB building is not only healthy for the individual, but also for the planet. Soil, a CEBs primary ingredient, is a renewable, non-toxic natural resource. Requiring less transportation of materials, CEBs have a lower embodied energy than conventional building materials. It takes many times more energy to make concrete than it does to make comparable amounts of CEBs. Cement is made under extremely high heat and the pollution from manufacture of cement is a major contributor to global warming. Using wood for buildings or to fire bricks contributes to deforestation, which is a significant problem in much of the developing world. In addition to being good for the environment, energy savings are immediate because the thermal mass properties of CEBs results in lower heating and cooling requirements.

Q: How long does it take to build an Earth Block home?
A: It depends on the actual size, but a small home requires 5,000 CEBs and the hand-operated press can produce 100 CEBs per hour or about 800 CEBs per day, with a work crew of seven people. Therefore, with one hand press it would be possible to produce the CEBs for a house in a week. The actual construction time will depend on the size and experience of the crew, but efficiency can be maximized by training in the use of construction systems such as story poles and thin slurry.

Q: Are these structures strong?
A: Yes, both stabilized and unstabilized CEBs are appropriate for buildings and meet U.S. building code standards for compression and modulus of rupture tests. The durability of a CEB building will allow it to last for centuries! Ancient earthen structures still stand today in many parts of the world. The expected life span of a wood frame building is just 70 years. CEBs have proven to be waterproof, fireproof, bug proof and bulletproof, and with bamboo or rebar reinforcement, these structures can be built to resist earthquake damage in seismic zones.  CEBs) are an incredible building material.

This useful information has been provided by Instituto Tierra y Cal, A.C., a non-profit organization that envisions a global resurgence of healthful and sustainable rural communities.

Its mission: “to improve quality of life in low-income and marginalized rural communities by providing training and ongoing technical assistance in support of community-driven use and development of compressed earth block construction and other appropriate sustainable building and environmental technologies.”

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