Nowadays construction companies are more likely to build poured concrete foundations than foundations made of concrete blocks. Concrete poured has become more popular for a number of reasons. Wall forms that are quick to set up and taken down, concrete trucks that can travel almost everywhere, and modern pumps and admixtures which make "impossible pours' almost common.

Despite all the advantages mentioned in the previous paragraphs, concrete block has its place as an acceptable foundation material. When the foundation is small for a home addition, for example-a builder can save money by laying up blocks instead of subcontracting the work out to a foundation contractor. Additionally foundations for crawl spaces are able to be efficiently and quickly built with concrete block. For those who are DIYers with some masonry experience, this material provides an opportunity to complete the foundation block by block one time.

Before we dive into the "heavy" subject, it's worth clearing up some terminology. In the building industry concrete blocks are called "CMUs," short for concrete masonry units. Beyond the typical 16 x 8 x 8 in. concrete masonry contractor 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 specifically designed for commercial construction.

Concrete blocks are created using the same components that are used to make concrete walls: gravel (called aggregate) and sand Portland cement and water. Lightweight blocks are sometimes called cinder blocks because they contain fly ash (cinders) which is a byproduct of industrial combustion is utilized as a partial substitute for 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 it is true that a block foundation made of concrete isn't necessarily inferior to a poured concrete foundation, if it's been properly built. Both types of masonry need steel reinforcement and should be laid on a strong and stable foundation. Good drainage and damp proofing features are essential. If expansive soils or other outside forces damage the concrete block foundation, cracks typically appear in the mortar joints which separate individual blocks.