FAQ

Q: What are Earth Blocks?
A: Earth Blocks, or compressed earth blocks (CEBs), are machine-made adobes, a modern variation on an ancient building material. The blocks are typically composed of 60% soil with high clay content (30-35% is ideal), 35% sand, and 5% lime as a stabilizer to create a water-resistant block. The percentage of each ingredient will vary from region to region depending on soil composition. Each of our earth press machines uses a high pressure hydraulic ram to form approximately 7.5 blocks per minute or 450 blocks per hour.

Q: How are Earth Blocks different than adobes?
A: Sun-dried adobes are made by pouring a mixture of mud and straw into forms on the ground, with the frequent addition of asphalt emulsion, a petroleum by-product, as the most widely used stabilizer. The adobes cure in the sun for as little as two weeks before being used and considerably longer depending upon weather conditions, but do not reach full strength for at least 30 days. Among the reasons we prefer earth blocks is their consistent size and quality, the speed of production, and the more natural and non-toxic stabilizer. In addition, their uniform size makes for a more rapid building process, with associated savings in labor costs, as the courses of blocks are even and only a thin layer of slurry between courses is required as opposed to a thick mortar joint. Finally, earth blocks have a much higher PSI, a measure of compressive strength, than sun-dried adobes which typically average between 300 and 350 PSI. While sun-dried adobes are sufficiently strong enough to meet the state of New Mexico's code requirement of 300 PSI, Earth Blocks typically test out at over 750 PSI. Strengths as high as 1800 PSI have been recorded for stabilized Earth Blocks.

Q: What are the dimensions of Earth Blocks?
A: The different machines on the market today produce blocks of varying size. Our machines have the capacity to produce blocks with the following dimensions and weights:

10" × 14" × 4"- 40 lbs.
8" × 14" × 4"- 32 lbs.
7" × 14" × 4"- 28 lbs.
Note: thickness may be adjusted between 3" and 5"

Q: How much does an Earth Block building cost?
A: Building costs vary depending on site location, soil composition, and architectural design. If the site dirt is not suitable for making blocks, either dirt is trucked on site to make blocks or the blocks are made elsewhere and trucked to the site. Trucking costs for dirt or blocks can be very expensive depending on the location of the site and amount of dirt or number of blocks needed. The design of the building ultimately determines the number of blocks and man hours involved in construction. Curved walls, multiple stories, and eccentric details are more difficult to construct and may require highly skilled laborers, thus creating more labor costs.

Q: How do you figure the number of earth blocks needed?
A: Typically, 5,000 blocks are needed for the exterior of a 1,500 square foot, single-story structure. There are approximately 2.6 blocks per square foot of wall space in a 10" thick wall, and 3.6 blocks per square foot in a 14" wall. Deduct for doors and windows and add 5% for breakage.

Q: How much dirt do I needed?
A: For 10" blocks, each block weighs 40 pounds; 50 blocks = 1 ton/~ 65 blocks = 1 yard of dirt (±1.3 tons/yard depending on dirt composition and moisture content)

Q: How do I know if the site dirt is suitable for making Earth Blocks?
A: Soils need to be tested by a qualified testing laboratory to make an accurate analysis of whether or not it is useable for construction with Earth Block. The following four factors are important to consider:

" Plasticity Index - the percent of clay in the soil, a very important factor in determining the binding quality of the block, and the percentage of aggregate to be added
" Sieve Analysis - the granular distribution of the sample in terms of clay, sand, and gravel
" PSI - a measure of the compressive strength of the block which must meet code requirements
" Modulus of Rupture - a measurement of the resistance to fracture

A common general test is the cigar test. Take a handful of dirt, form it into the shape of a cigar, lay it on a flat surface and push it slowly over the edge. If the cigar stays intact for the first inch you may have soil worthy of making Earth Blocks.

Q: How does Earth Block construction compare to conventional building techniques?

A: An Earth Block building is not only healthy for the individual, but also for the planet. Dirt, an Earth Block's primary ingredient, is a renewable, non-toxic natural resource. Earth Block walls are virtually breathable, soundproof, bug-proof, fireproof, and even bulletproof! Requiring less transportation of materials than conventional construction methods, Earth Blocks have a lower embodied energy than conventional building materials. Energy savings are immediate with thermal mass equating to lowered heating and cooling requirements. The durability of an Earth Block building means it will last for centuries! Ancient earthen structures still stand today in certain parts of the world. The expected life span of a wood frame building is just 70 years.

Q: What does it mean to have a 'breathable' wall?
A: A breathable wall is porous and allows indoor vapors, toxins, odors, and moisture or humidity to pass slowly through the wall to the outside, as well as fresh air from the outdoors to enter the building, thereby maintaining a healthier indoor environment. In addition to promoting the health of the occupants and facilitating temperature control, the longevity of the wall is enhanced by its porosity and flexibility. Insulation and other synthetic materials such as stucco applied to Earth Block walls will hinder its breathablity, whereas lime or clay plasters do not.

Q: What is thermal mass?
A: Thermal mass is the ability of a material to retain heat. The thick walls of an Earth Block building create thermal mass, protecting the occupants from extreme temperatures with a building that stays cool in the summer and warm in the winter. Heating and cooling requirements in an Earth Block building are substantially reduced in an Earth Block home.

Q: What is embodied energy?
A: Embodied energy is the total amount of energy required to manufacture a product; including the initial removal of the raw material, transportation, processing, distribution, and its final usage. The more embodied energy in a product the greater the carbon dioxide (CO2) emissions, and thus, contribution to the greenhouse effect and global warming. Although the block machine requires diesel fuel, only ten gallons are needed to produce 3,000 blocks. Moreover, substituting bio-diesel reduces pollution and makes use of a waste product. Compared to a 10'× 10' wood-framed wall that has an embodied energy equivalent to 6 gallons of gasoline, an adobe wall of the same size only requires about 0.2 gallons of gasoline.

Q: Are Earth Blocks safe in earthquake-prone areas?
A: Special techniques may be used to resist ground movement in seismic zones, including horizontal wire ladder reinforcement, vertical steel-reinforced concrete columns, and through-tied galvanized stucco wire on both sides of the walls. Shake table tests in Berkeley, California and Peru have clearly demonstrated the effectiveness of these procedures.

Q: Why stabilize Earth Blocks?
A: Using 5-8% lime or Portland cement stabilizes the blocks and eliminates concerns about potential water damage during construction. Concrete footers keep the blocks from coming in contact with the ground and a cement bond beam protects the top. Stabilized Earth Blocks are water-resistant, but need protective plastering to be considered completely weather-proof. The compressive strength (PSI) of the blocks is also greatly enhanced by stabilization.

Q: Which stabilizer is best?
A: We believe that lime is a superior product. However, in many instances Portland cement is used as a stabilizer and is very effective. Unlike cement, lime is a more natural product, more breathable, has self-healing properties which aid in the repair of any cracks which may appear, has a lower embodied energy, and even absorbs CO2.

Q: What is the R-value and U-value of Earth Blocks?
A: The R-value, or resistance to heat flow, is the most common used measurement for determining building material's insulating properties. The greater the R-value of a material, the better it is at resisting heat loss (or heat gain). An earth block wall has very little insulative or R-value. Although proponents of other wall systems point to a high R-value as advantageous due to the ability to resist heat loss or gain, an earthen structure with breathable walls has the advantage of U-value (BTU/hr/ft2/°F). The U-value is based on the materials thermal transmittance abilities given a difference between the interior and outside temperatures. The lesser the U-factor of a material, the better it is at transmitting heat. Consequently, the interior temperature of the building changes slowly. A 16" adobe wall has a U-factor of .163 compared to .490 for concrete blocks.

Q: Does an Earth Block building require insulation?
A: In extreme climates Earth Block buildings can be double walled with an air space in between that is either left empty or filled with dirt or foam. Walls can be covered with foam sheets or sprayed foam for added temperature maintenance on those sides of the building that are exposed to extreme temperatures.

Q: Where can I see photos of the Earth Block process?
A: Go to: http://www.flickr.com/photos/tierraycal/sets. If the link isn't working, please cut and paste the URL into your browser.

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Earth Block, Inc.

P.O. Box 3605
Pagosa Springs, CO 81147
Jim or Nora Hallock
Phone: 970-883-2456
Email: earthblock@juno.com