Making Compressed Earth Blocks

The Renaissance of Natural Construction

Compressed earth blocks are very much the same as adobe bricks although the latter conjures up images of Mexican Pueblo housing designs.  Compressed earth blocks are a modern version of ancient building system. The oldest, continuously lived in earthen masonry building, is in the Western Hemisphere in the Lima, Peru basin and is over 3,500 years old.

Traditional adobe bricks were made from slurry of clay soil, straw and manure placed in a mold to dry in the sun. The blocks were very irregular in size therefore needing a thick bed of mortar to create a wall.

Modern Compressed earth block machines have made the process much faster and more convenient. These blocks are very consistent in size enabling us to lay up the blocks using thin slurry in-between each layer.  The material used to make the blocks is quite accessible. Geological Survey show that 65-70 percent of the soil present on the Earth's surface is a likely candidate for making compressed soil blocks.

At FifthWind we start with clay soil that is dug from the farm which at the same time is creating a pond. This type of soil is found in most parts of southern Ontario. It is the cheapest of the soils in the building industry and most undesirable but, for our purpose, it is ideal. We have learned to overcome the undesirable characteristics through a process of trial and error. Since clay dries in hard clumps we start by breaking it up to a fine powder using the soil processor. It screens out the biggest rocks and a hammer mill breaks up the rest of the soil.

When we first started the research our intention was to use un-stabilized compressed earth blocks (CEB) but we have come to the conclusion in our climate it is difficult. We now add 5 percent stabilizer of cement or a 50-50 cement-lime combo to the soil. That small amount is enough to keep from eroding during bad weather conditions: rain and freeze and thaw. The mixing is accomplished using a one yard concrete mixer where we add the moisture and the 5 percent cement. The mix is dry to the touch but is able to compact enough to stay together by squeezing it in one hand.

The well mixed soil is transported by Bobcat from the concrete mixer to the compressed earth block machine. The hydraulically machine is capable to produce 360 blocks per hour. The blocks are then stacked and air dried; and ready for use within a day.