Nowadays construction companies tend to prefer foundations made of concrete poured than those constructed using concrete blocks. Poured concrete is becoming more popular for a number of reasons, including wall forms that can be quickly set up and taken down as well as concrete trucks that are able to go almost anywhere as well as modern pumps and admixtures that create "impossible pours" almost routine.

Despite all the advantages mentioned above, concrete block can be used as a viable foundation material. When the foundation is small for a home addition, for instance, a builder can save money by laying up blocks instead of subcontracting the work to a foundation contractor. Additionally foundations for crawl spaces can be quickly and economically built with concrete block. If you are a DIYer with some masonry experience, this material provides the chance to build the foundation block by block each step.

Before we dive into this "heavy" topic it's helpful to know some terminology. In the construction industry concrete blocks are called "CMUs," short for concrete masonry units. Beyond the typical 16x8x8 in. concrete block that is sold by the majority of stores for home use, the variety of CMU dimensions, shapes and the finishes on their surfaces is simply amazing. A majority of the CMUs are intended for commercial construction.

Concrete blocks are created using the same components found in concrete walls, which are gravel (called aggregate) and sand Portland cement and water. Blocks that are light weight can be referred to as cinder blocks because fly ash (cinders) which is a byproduct of industrial combustion is utilized to substitute heavier ingredients like sand and aggregate. The hollow cores found in many CMUs allow the block to be cheaper and easier to handle. They can also be filled with cement sand or foam insulation to increase the durability, thermal mass or insulation value.

Contrary to popular belief the concrete block foundation isn't inherently inferior to a concrete foundation, providing that it's properly constructed. Both kinds of masonry require steel reinforcement, and they must be placed on a sturdy, stable footing. A good drainage system and Phoenix damp proofing details are crucial. When expansive soils or other external forces cause damage to a concrete block foundation cracks are typically seen along the mortar joints that divide the blocks.