Types of Concrete Footings
You have probably heard the phrase, "Built on a solid foundation." Well, the phrase is literally taken from a building that can withstand the test of weather and time and minimize the settling of the building. All buildings settle to some degree over time. But when it is sudden and uneven, settling can cause structural damage. A solid foundation must be built on solid footings. Does this Spark an idea?
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Footings
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Footings come in various types, many of them premade. They are buried in the ground or rest on the ground, depending on their use and load-bearing needs. The type of footing used depends on the compaction density of the soil, where the structure will rest, whether the location ever experiences frost and whether the building is in a coastal area.
General residential buildings
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For most homes and light construction, where the soil is fairly compact, a shallow footing is used because it's the most economical and will support the required load. However, where soil compaction or stability is an issue, a deeper footing is usually needed.
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For trickier construction areas
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Coastal areas subject to flooding require deep pilings to assure the stability of the buildings. Concrete or pressure-treated lumber is usually used. A shallow footing isn't sturdy enough to withstand the rushing water pressure of floods. Deep footings are more expensive than shallow ones.
Frost
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In colder climates, the footing must be below what is called the frost line. That is the depth of the soil where it can still both freeze and thaw. If the footing is subject to yearly freeze-and-thaw cycles its structural integrity can quickly diminish. The same is true of the building and the foundation on which it sits. In most areas, local zoning laws dictate the depth at which a footing must be built.
Footing placement can get tricky
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Placement of the footing depends on the design of the structure and the type of foundation. Some buildings are designed to distribute the weight evenly, others not as much. How the building is engineered dictates where and what kind of footing is needed.
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References
- Photo Credit A basic shallow "T" footing; credit, Concreteworkd.com
