One out of every three homes on a slab fails due to an existing foundation issue. There are two types of foundations – those that contain masonry blocks and those that are built with concrete slabs. A building with a concrete slab foundation, or a building where the footing and the footing of the slab are poured directly into the soil. The framing of each foundation type will generally be the same whether the building uses masonry block construction or poured concrete. Masonry block and poured concrete foundations each stand on their own separately from the main frame.
The most common theme in older homes with strong foundations and lots masonry construction is the lack of adequate backfill area. The lack of backfill causes the walls to begin to crack and soften, allowing moisture to enter. This is usually caused by an inadequate area of dirt and rock aggregate; either soil that has too much clay or soil that has been washed away from heavy rainfalls over a long period of time. This type of water retention is what causes the walls to start to crack and loosen over time. Cracking in the foundation walls of a new home is usually from a lack of soil backfill or a poor placement or construction of the foundation. In this case, the settlement will have caused the soil to smooth and heave. This water should have been absorbed during the construction of the foundation, however, the excess water or water that was absorbed over time is what caused the cracking in the walls.
When a home is expected to have concrete foundations, then the type of soil underneath the property should be known, whether it is going to be built on fill or dirt or clay. If the property is a new natural friction built up area then the soil around the foundation should be inspected for any wetness and clay content that is still on top of the ground. If the soil is compacted or sits over a period of time, the foundation may find it very difficult to develop rigid mechanical retention. If the property has had a water or moisture problem in prior years, a thorough soil investigation should be done by a professional structural engineer to ensure that the necessary steps are taken to minimize the impact on the structure, especially the foundation. It is also important to determine if the pre-existing foundation was ever properly built on the property.