What Are the Most Common Types of Foundations?

The quality of a structure’s foundation goes a long way toward ensuring its long-term structural soundness. There are several different types of foundations that may be used depending on the kind of building and the geological characteristics of the construction site.

Let’s take a look at the most common types of foundation in Tennessee, split into two categories: shallow foundations and deep foundations.

Shallow foundations

· Individual/isolated footing foundations: This type of foundation features a square individual footing used to carry loads from columns. The size of the individual footing is based on the load of the column and the capacity of the soil in the area to safely bear a load.

· Combined footing foundations: This type of foundation is similar to individual footing foundations, but is used when there are two or more columns in close contact with each other, requiring footings that overlap. The result is the use of rectangular footings to support the loads carried by columns.

· Raft/mat foundations: Raft and mat foundations are spread across the entire area of a building to support heavy loads from walls and columns. This type of foundation will be used where there are very high loads from the structure on columns and walls, and helps prevent settlement of individual footings. It is ideal for soils with bearing capacity less than suitable for spread footings and wall footings.

· Spread/strip/wall footings: Spread footings are those that have a base wider than what would be typical of a load-bearing wall foundation, which helps spread out the weight of the building structure over a greater area. Spread and wall footings are used for individual columns, bridge piers and walls when the bearing layer of soil is within 10 feet of the ground surface.

Deep foundations

· Drilled shafts/caisson foundations: Drilled shaft foundations are also referred to as “caissons,” and are designed to serve as high-capacity, cast-in-site foundations. They resist loads from heavy structures through shaft and/or toe resistance, and are created with the use of an auger. They are used when the depth of hard strata that exists below the surface is within 10 to 100 meters (25 to 300 feet). This type of foundation is not suitable if there are deep deposits of soft clays or water-bearing granular soils, or if it will be difficult to stabilize caving formations.

· Pile foundations: Pile foundations exist to transfer heavy loads from a structure into a hard rock strata located deep down below the surface of the ground. They are an alternative option when spread footings or mat footings cannot be used. In many cases, they are also used to add extra protections against earthquakes or heavy winds, or when soil conditions near the surface are not suitable for heavier loads. This type of foundation helps prevent differential settlement, and will resist loads through skin friction and end bearing.

For more information about some of the most common kinds of deep and shallow foundations you’re likely to encounter in Tennessee, contact the team at Warrior Precast LLC today.

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