A foundation is a necessary structure in construction that supports and transfers the weight of a building to the earth. A shallow foundation is near the earth’s surface, while deep foundations are placed at greater depths in the earth. You must understand several differences between shallow and deep foundations to determine which is best for your construction project.

Foundation Depth and Feasibility

When looking at the depth of the two foundations, shallow structures are less than six feet beneath the earth’s surface, and deep structures need to go beyond ten feet below the earth to be considered a deep foundation. Typically, the shallower a foundation is, the easier it will be to construct, and the deeper it is, the more complex it will become.

Foundation Mechanisms of Load Transfer and the Type of Auger Tooling Used

The mechanisms of load transfer relate to how the foundation supports the weight of the structure built on top of it. For shallow foundations, the primary load transfers by end bearing. Deep foundations use the same mechanism with added skin friction to support the weight of their structures.

End bearing is when the structure’s weight is distributed from the topsoil to a stronger rock or dense sand/gravel. You will need foundation drilling tools to reach the correct depth for deeper foundations. Skin friction is when there is friction between the piles you place in the ground for support and the soil surrounding it.

As for the type of augers you would use to drill foundations, the tool needs to be 50–70 inches tall for shallow foundations. Deeper foundations are slightly different and require a CFA string that is 10–30 feet tall and pinned by couplers to make one continuous flight auger that reaches the correct depth in the earth.

Advantages of Each Foundation

Shallow foundations support smaller structures because they require fewer construction materials and less labor to build. This also means it’s more affordable to build this type of foundation.

Deeper foundations have the advantage when shallow structures are not possible. Deep structures provide lateral support and resist uplift from the pressure of the ground, wind, or water. The deeper the foundation, the larger the load they can carry, which can prove highly beneficial.

Disadvantages of Each Foundation

Shallow foundations cannot support lateral loads; they can settle and are usually only stable enough for lightweight buildings.

Deeper foundations require more labor to build due to the complexity of the construction process. Therefore, it’s time-consuming to build this type of foundation, and they’re not very flexible regarding the pressure you place on the underlying soil.

There are clearly various differences between shallow and deep foundations, and each option has its own benefits regarding the type of structures it can support. If you’re building a taller structure, a deeper foundation can provide more stability and support than a shallow foundation. Keep the configurations of each structure in mind to better determine which is suitable for your construction project.