Frequently asked questions - Compressed Earth Blocks

A line of compressed earth blocks coming out of an AECT CEB machine

What is a CEB?

A CEB is a compressed earth block. They are produced by compressing earth at about 1,000 to 1,800 PSI.

What are CEBs used for?

You can use CEBs to build just about anything you can think of: High-end Houses, Low-cost Housing, Commercial Buildings, Barns, Garages, Outdoor Living Spaces, Walkways, Driveways, Fireplaces, Ovens, Perimeter Walls. With CEBs, you can let your imagination run wild! 

Why are CEBs so popular?

There is no better building material in the world besides CEBs. They are durable, fireproof, tornado proof, eco-friendly, readily available, beautiful, natural, water resistant (when stabilized), insect proof, bullet proof, and provide great insulation. There is really no down side to CEBs as a building material, so it’s no surprise that when people find out about them, they ask “why doesn’t every build with CEBs?”

What sizes do CEBs come in?

AECT machines can make the following sizes of CEB:

4” x 12” (thickness 2” to 4.5”)

6” x 12” (thickness 2” to 4.5”)

6”x 12” with holes (thickness 2” to 4.5”)

7” x 14” (thickness 2” to 4.5”)

7” x 14” interlocking with holes (thickness 3” to 5”)

8” x 14” (thickness 2” to 4.5”)

10” x 14” (thickness 2” to 4.5”)

What is the difference between an un-stabilized CEB and a stabilized CEB?

Un-stabilized CEBs are made only with natural earthen material (clay, sand, aggregate, silt). These blocks are not water resistant on their own, so once built into a wall, they will need to be covered with a porch roof or some kind of coating, such as lime, stucco, or paint.

Stabilized CEBs are made with about 92% natural earthen material and about 8% cement, lime, or fly ash. These blocks have the advantage over un-stabilized blocks that they are completely water resistant.  

A comparison of un-stabilized CEBs vs. stabilized CEBs is shown in the table below.

Chart comparing attributes of stabilized and un-stabilized CEBs

Is there a specific type of earth that will work to make CEBs?

A wide range of earth is suitable to make great CEBs. In fact, about 70% of the earthen material on this planet will work. There are two hard requirements, however: The first requirement is that you should avoid organic material in your earth mix, as it will not compress (this is easily avoided by pulling your material from at least 12” below the ground surface).  The second requirement is that you need some clay in your earthen material. For Un-stabilized CEBs, it’s ideal that your earth contains about 20% to 30% clay. For cement-stabilized CEBs, you only want about 10% to 15% clay and a higher content of sand, because it’s the sand that the cement bonds with. 

How do I know if my earthen material will work?

You will have to do some testing up front to get to the right recipe for your CEB material. If you want to produce cement-stabilized CEBs and find that your earth has a high (20% plus) clay percentage, you may want to search for a soil with less clay and more sand…or you may want to bring in sand to augment your high-clay material. You will also want to make some sample blocks to determine whether or not your earthen material will make good CEBs. We sell a small block press that works perfect for this function: 

We can also help you through the material testing process as part of our consulting service offering: 

How much moisture should be in my earthen material?

Make no mistake…the moisture content of your earthen material is critical to making great CEBs. The moisture level in your material needs to be about 5% to 10%, depending on the type of soil. There are techniques to determining the correct moisture level, and we can offer guidance on how to appropriately control the moisture content in your earthen material as part of our consulting service offering: 

Why do I need a mixer?

Now that you understand the importance of having the right clay, sand, cement, and moisture in your earth mix, it’s easy to understand why using a capable earth mixer is so important. Regardless of whether you are producing un-stabilized blocks or stabilized blocks, you will need one of our Mega Mixers if you want to get the full capability out of your AECT CEB machine.  The specs and a video of our mixer in use is shown here: 

A CEB doorway, complete with earth block arch

How can I get some CEBs?

With AECT’s wide range of product and service offerings, there are many options for someone who wants to build with CEBs. You can buy one of our machines and build your own blocks: 

You can rent our machinery and either build your own blocks or have us build them for you: 

Or you can buy the CEBs right from us:

How much does it cost to build a CEB home?

Keep in mind that the walls of a home make up only about 17% of the build cost, so depending on the finish-out and location of your home, the entire cost will be very comparable to that of standard building materials ($110 to $350 per square foot).  While CEBs are a premium building material, the walls of your home will not cost much more when compared to inferior standard building materials (cinder blocks, stick-frame, etc.)…yet you will have a home that is fire proof, tornado proof, natural, durable, and beautiful!  And because of the high thermal mass that CEBs provide, your AC and heating bills will be only a fraction of what they would have been with traditional building materials. You could end up saving over $100,000 in energy costs over the lifetime of your home!