Frequently Asked Questions

What is the optimum fill material for the blocks?

We have conducted numerous surveys and have analyzed soil maps and actual samples from all over the globe to determine what type of soil works best in our machine. Simply stated, over 85% of the world's soil will work. We take regular soil right out of the ground, screen everything 1" greater out, and use the rest to make our blocks.

Must there be a high clay content for the blocks to maintain their shape?

The critical element that must be present, regardless of the overall makeup of the soil used, is clay. Even under extreme pressures, 100% silica sand and rock will not bind together to form a block. The makeup of an ideal soil would contain approximately 20-30% clay. However, we have successfully produced blocks from soil that contained 10-20% clay. While we can also work with higher clay contents all the way up to 90%, we sometimes have to add aggregate or rough, unwashed sand to that source to create a good, strong block.

What other materials / soil types may be used in its operation whilst maintaining structural integrity?

Most soils are made up of fine silt or fine clay, clay, aggregate, heavy aggregate, and rock or pebbles. Our machines are very forgiving in terms of what soil type works best. We have manufactured blocks in sandy soils, sticky clay soils and everything in between. So long as we have 20-30% clay content present, we can usually make a good block regardless of what the remaining soil (absent rocks) consists of.

What are the degradation rates in dry, wet and windy conditions?

Dry or windy conditions have no affect on the blocks. If the proposed construction site does not have any protection from the elements and it is located in a wet or rainy area, it will be necessary to stabilize the blocks in some manner. There are a number of ways to accomplish this. One is to mix approximately 5-8% Portland cement into the dry soil and then compress that cement infused soil into blocks. Those blocks would then need to be wetted for a period of 4-6 days to allow the cement to set. Those blocks would then hold up extremely well to moisture and rain. Another way to stabilize the blocks is to add and mix hydrated lime into the dry soil to a high ph level prior to compression. Once the lime-infused blocks are compressed, they can be laid directly into the wall. After the walls and structure are built, a lime wash or lime plaster can be applied similar to conventional stucco. Once this has been accomplished, these blocks will be impervious to moisture, rain, and erosion. Lime stabilization is usually less expensive than cement stabilization and doesn't require that the blocks be turned over and handled again while wetting them. Cement stabilization takes less field knowledge than working with lime as you can simply use a percentage calculation as opposed to the testing required to adjust the ph level when using lime. You can also apply conventional cement stucco material over the soil-only blocks. While there are a number of waterproof paints and coverings that will adhere to our blocks, these products are usually quite expensive and not cost effective for most applications. Finally, if the walls will have a cover similar to a Barn pole roof, stucco finish or have a bona fide roof system in place - you wouldn't need to do anything to the soil only blocks. They would hold up quite well in a protective environment.

What is the lifespan of the different types of block in the aforementioned conditions?

History shows us that adobe and soil buildings have endured for hundreds, if not thousands, of years. For blocks that are not stabilized, you will need to have them protected from the elements if you are operating in wet conditions. For areas where temperatures can reach 115 degrees or higher in a dry, arid desert for most of the year, blocks can be placed right out in the elements with very little degradation. Even if the top layer becomes worn due to an unseasonable rain, you can simple replace the damaged blocks and add a new layer of blocks. If you stabilize the blocks via either method described, they will unquestionably last a very, very long time.

What is the servicing / maintenance requirement of the equipment?

The equipment requires the same type of regular maintenance that a front end loader or bulldozer would normally require. It has several grease fittings that need to be hit a couple of times a day and the various temperature and pressure gauges need to be monitored while operating. Each model requires about 45 minutes per day to service and maintain. We have units currently operating in the field that have produced over one (1) million blocks and are still operating with most of the original components still in place and functioning as intended.

How much fuel is consumed per hour of operation?

All of our units use approximately 1.5 gallon of diesel per hour of operation.

What are the shipping and loading considerations for the two larger models?

Both machines can be containerized into international shipping containers. The Series 960 unit weighs approximately 9,800 lbs. and is 8.33 ft. wide by 16.5 ft long by 8 ft. high. The Series 480 machine weighs 5,600 lbs. and is 7.38 ft. wide by 13.67 ft. long by 6.83 ft. high. Both units can be towed behind a heavy duty pickup or similar vehicle. The equipment can be licensed for towing and legal highway speed limits can be attained with no problems.

Can the equipment be lifted by helicopter?

The units come fitted with four (4) lifting hooks and can be lifted with helicopters specifically designed to transport such items.

How many people are needed to handle the blocks as they come off the conveyer belt?

You would normally need a crew of around 4 - 5 handling the blocks as they come off the machine. The large machine (Series 960) produces up to 960 blocks per hour or one every 3.5 seconds. The mid-sized unit (Series 480) is rated to produce up to 480 blocks per hour or one every 8 seconds. The smallest model (Series 240) produces over 240 blocks per hour or one every 18 seconds. Working two men on each side of the conveyor and alternating the output keeps things moving without stressing the block handlers too much. A standard pallet holds 96 blocks and the standard size blocks produced by the Series 960 and Series 480 models are 14" x 10" x 3.5" weighing 36-38 lbs each. The standard size blocks produced by the Series 240 machine are 12" x 6" x 3.5" and weigh approximately 18-20 pounds each. After the machines are started, they operate automatically and will continue to produce blocks so long as the hopper stays full of soil. You may pause the machines at any time but you cannot slow them down to produce fewer blocks per hour - they are either in a full operating mode or in paused or stopped mode.

What are the soil volume requirements to produce a block?

We can produce approximately fifty (50) 14' x 10' x 3.5' compressed blocks with one (1) cubic yard of soil. The capacity of a standard sized dump truck is approximately 20 cubic yards.

How do I determine the number of soil blocks required to build a wall or structure?

Follow the formula below for the 14" x 10" blocks:
  • For a 10" thick wall: = 2.7 blocks per square foot of wall space.
  • For a 14" thick wall: = 3.4 blocks per square foot of wall space. Example: 10 ft. length x 8 ft. height, 10" wall = 80 sq. ft. x 2.7 = 216 blocks.

If using the 12" x 6" blocks from the Series 240 model, follow the formula below.

  • For a 12" wall with 3" thick blocks = 8.0 blocks per square foot of wall space.
  • For a 12" wall with 4" thick blocks - 6.0 blocks pers square foot of wall space.
  • To determine the approximate number of soil blocks that will be required to build a wall, using 12" x 6" blocks, follow the formula below.

  • For a 12" thick wall: = 5.9 blocks per square foot of wall space.
  • NOTE: Do not deduct for the area to be taken up by windows or doors regardless of which size block is being used.

What ingredients are required for the slurry (mortar mix)?

We use the exact same soil for the slurry as is used for the blocks. The soil is screened down to remove any rocks or pebbles and we then make a wet, thin, pancake batter-like mixture. This slurry can be mixed in a wheelbarrow or motar mixer. It is important to remember to have the water first and add soil to it to create the desired consistency. The slurry is applied via a coffee can or similar means directly onto the lower block course and the blocks are placed on top just like you would with conventional bricks. The slurry creates a homogeneous bond between the two block layers much like pressing two bars of soap together in a shower. On a hot day in central Texas, the blocks will bond together in just a few minutes, requiring a hammer and chisel to dislodge them.

Is there a season/weather period recommended?

It is impossible to make blocks in rain unless you have moved the soil and the machine into a warehouse or a covered area. The blocks can be produced and laid into a wall in cold weather as long as the mortar mix is not frozen. Heat has no effect on the blocks or the mortar other than to dry things faster. If the soil is extremely dry, a light fogging of the soil with water will produce the desired moisture content. Most soil has adequate moisture and doesn't require additional moisture. We have operated the equipment in 124+ degree heat and have had no problems with the equipment or the blocks.

Are the compressed dirt blocks rated as an authorized construction material?

Adobe construction is an accepted and approved method of construction throughout most of the Southwestern areas of the US. Our compressed soil blocks exceed (usually by 3-4 times) the building strength of material standards for non-fired masonry construction in the United States. Our soil blocks have exceeded, in all cases, the Uniform Building Code (UBC), the Southern Building Code, the HUD Standards, the Farmers Home Administration Standards, the Veterans Administration Standards, the FHA Building Material and Construction Standards, and The International Building Code (IBC). The IBC spells out the specific guidelines that should be adhered to throughout the entire country. Another good source of information is the New Mexico Earthen Building Code which regulates the construction of new buildings made of adobe, rammed earth, and compressed earthen blocks. Keep in mind that these blocks are load bearing - not filler blocks.

The minimum standards for adobe construction as per the Uniform Building Code is: COMPRESSIVE STRENGTH 300 psi Minimum Standard LEGI Compressed Soil Only Blocks 1,000 - 1,500 psi LEGI Cement / Lime Stabilized Blocks 2,500 - 3,900 psi MODULUS OF RUPTURE 50 psi Minimum Standard LEGI Compressed Soil Only Blocks 70 - 140 psi LEGI Cement / Lime Stabilized Blocks 250 - 600 psi

Our Solutions

    1 LEGI 480 Series

    The LEGI Series 480 Compressed Soil Block Machine is fully automated and produces up to 480 compressed soil blocks per hour of load bearing, non-fired, structural blocks for all kinds of construction projects. The machine can be set to vary the thickness of the blocks from 2.0 to 4.5 inches. Soil can be loaded with a front-end loader or bobcat type loader.

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    2 LEGI 240 Series

    The LEGI Series 240 Compressed Soil Block Machine is very light and can be hauled behind a farm tractor, car, or compact pickup truck equipped with a ball hitch. The machine produces in excess of 240 compressed soil blocks per hour and has been designed for use in extreme remote areas without access to front end loader. This model can also be set to vary the thickness of the blocks from 2.0 to 4.5 inches. The machine is loaded with shovels or buckets and can be easily moved by hand around the construction site.

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    3 LEGI 20 SMM

    The LEGI Series 20 Soil Mixing Machine is capable of mixing soil and other materials at a variable rate up to 20+ yards per hour.  Moisture is added as required through 8 nozzles that can be controlled by the operator for desired ratios.  The additives such as portland cement, lime, fly ash and moisture can all be controlled to operator's specification.  The LEGI Series 20 SMM additive hopper has a 23 cubic foot capacity for materials such as fly ash, cement, or lime. The machine will process enough soil to feed two LEGI Series 480 Compressed Soil Block Machines.

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    4 LEGI 10 SMM

    The LEGI Series 10 Soil Mixing Machine is capable of mixing soil and other materials at a variable rate up to 10+ yards per hour. Moisture is added as required through 6 nozzles that can be controlled by the operator for desired ratios. The additives such as portland cement, lime, fly ash and moisture can all be controlled to operator's specification. The machine will process enough soil to feed one (1) LEGI Series 480 Compressed Soil Block Machine.

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