The decision of which type of foundation to utilize should be made according to the capacity of the soil at the building site to bear the weight of the structure that will be built upon it. Adequately sized footings, as well as a strong foundation, prevent too much settling of the ground and these two factors are critical to the stability performance of structures built upon them.
Two Basic Types of Foundations
Foundations usually are divided into two fundamental groups: shallow or deep. The classification of the foundation system depends largely on how deep the load transfer member reaches beneath the super structure and what kind of load transfer is being used.
The correct type of foundation therefore is dependant on how strong and how easily compressed the building site’s soil is, how the loads on it are going to be constructed, and the total amount of settlement that will predictably occur.
Shallow foundations provide the typical system used on most residential building sites. Usually, the weight bearing capacity of the soil does not pose any problems, and this type of foundation proves to be the most economical system. Light commercial building sites that are going to have raised floors are also likely candidates for shallow foundations.
However, where poor soil conditions exist, deeper foundations should be utilized. Deep foundation systems include those that use concrete piers. This type of foundation is often seen in coastal areas where the likelihood of hazardous flooding is high and the foundation of buildings needs to be above the base flood elevations to comply with flood insurance programs. Sometimes concrete pier foundations are also used for outdoor structures like decks and for porches adjoining a home.
Most often constructed with reinforced concrete block that is supported by either pad footings or spread footings that are also reinforced and made of concrete, concrete pier foundations rely on pier spacing determined by floor framing arrangement. Where the load-bearing walls and partitions will be are of great importance. The spacing of concrete piers is usually from eight to twelve feet as a common practice.
Pad footings (sometimes called “spot” footings) that are used to support an individual concrete pier, are usually a block of reinforced concrete – two feet square and ten to twelve inches thick. These pads are typically rated at three thousand to five thousand pounds per square inch of compression in order to provide more-than-adequate support and stability for the concrete pier foundation.
For Professionals Only
If you are intending on building a foundation for something larger than a garden shed or outdoor deck, you should leave this up to an expert. Unless you are professionally trained to install a concrete pier foundation, it’s best to leave this type of project up to someone who is. Since the foundation of your structure dictates the reliability of even the best-built project, don’t take chances.
Although engineers don’t usually actually build foundations, they do provide the expertise and knowledge that foundation companies rely upon to give quality service for customers. You can find qualified professional foundation companies in your area through the phone book or by an online search.