What are concrete piers?

Concrete piers are a type of foundation designed to support structures that may experience flooding or soil that produces lateral movement. Although a concrete slab is probably the simplest type of foundation, a concrete pier comes at a close second. Concrete piers are cylinders of concrete drilled into the ground and then attached to a structure above.

You can use concrete piers either as a choice for a new foundation or as a mechanism to rescue a subsiding foundation. Either way, they provide an extremely long-lasting means of supporting a structure.

This guide will walk you through all of the key aspects of a concrete pier foundation so that you can undertake your construction project with all the information you need to commission an enduring and solid structure.

Overview

The structure of a home is only as strong as its foundation. While foundations are installed with the intention of lasting for generations, the reality is often somewhat different. Poor-draining soil, sloped ground, or just age can all lead to foundations losing their solidity.

Concrete piers are one of many types of foundations available. They tend to be used in coastal areas due to the fact that they help with high water levels. Concrete slab foundations (which are the most common overall foundation types) don’t fare as well in areas that either have a high water table or are susceptible to flooding. In these areas, concrete piers provide a better long-term option.

Concrete pier foundations are usually built to give a 1-1.5 foot gap above the ground. This is used to prevent any moisture damage to a wooden structure. Not only does it mean the structure is less likely to be flooded, but allowing the air to pass underneath allows air to circulate, preventing damage from residual moisture. The piers can be any shape, but most commonly are rectangular, circular, or square, and usually measure 6, 8, 10, or 16 inches in diameter.

They are drilled into the ground to a level below where the ground freezes (known as the freezing depth), which is usually at a level of five or six feet below the ground level. They provide an extremely strong and enduring foundation for a home and can last as long as any other type of foundation.

How are Concrete Piers Installed?

Concrete piers are installed in the same way whether they are being used to reinforce an existing foundation or are being installed for the first time in a brand new building.

The first step is to drill or dig a hole roughly one foot in diameter (larger if you’re planning on using 16-inch piers). The depth depends on the freezing depth of the soil but can be anywhere from 5 feet to 20 feet underneath the home. You may need to undertake a soil survey before work can begin. The surveyor will be able to tell you the correct depth to install the piers.
The concrete is then poured into the holes. In some cases, the concrete may be reinforced with steel bars. However, in most cases, this is not necessary. The concrete can take up to seven days to fully cure. Once they have cured, they are ready to take the weight of the house.

If this is a new build, the structure can then be built directly on top of the piers. If it is a reinforcement, then a hydraulic jack will raise the structure to the required height. There may be a need for concrete or steel spacers to close the precise gap between the pier and the structure.

The actual number of concrete piers will depend on the size of the structure. For small repairs, you may only need one pier. For larger structures and new buildings, you may need upwards of ten piers to support the entire weight.

WHAT ARE THE ADVANTAGES OF CONCRETE PIERS?

Pier foundations have a number of advantages over other types of foundations. After all, there’s a reason why they are one of the most common types of foundation. As mentioned above, pier foundations have a significant advantage over concrete slabs in coastal areas and regions prone to flooding. This obviously encompasses a significant amount of the United States. However, there are other advantages. Some of these are as follows:

They use readily available materials (i.e., concrete, and not much else)

They are extremely easy to install and often don’t need any heavy excavation (it is possible to dig out the shafts for the piers using a shovel).

The foundation inspection is far easier since parts of the foundation stand above ground

If you have plumbing or electrical problems, it’s relatively easy for utility workers to access the space where the problem is occurring.

Concrete piers are relatively eco-friendly and can be uninstalled with no long-term impact on the surrounding soil environment.

The increased airflow underneath the home reduces heating bills in the winter and A/C bills in the summer.

It’s easily possible to increase the bearing capacity of the foundations with a little bit of under-reaming

Raising the structure off the ground diminishes the likelihood of flooding.

The structure dries easily in case of flooding due to the air circulating underneath.

Concrete piers are relatively quick to install (and dry faster than a concrete slab).

Of course, there are many more advantages that may fit your specific circumstances. However, the above list covers some of the most common benefits that a concrete pier foundation has over other types of foundation.

When are Concrete Piers Used?

There are a few different circumstances in which concrete piers are the best option for supporting a foundation. Most of these are for brand new buildings, although concrete piers can also be a means of reinforcing a subsiding building. However, the following situations are ones in which concrete piers are preferable to a slab or other type of foundation:

When there are lateral forces that push against the foundation (such as when the building is on a steep slope).
When the soil conditions are any of the following: prone to erosion, likely to uplift, weak soil, or expansive areas of soil. In these situations, concrete piers effectively operate as an insurance policy against changes in the forces operating upon a foundation.
When you need deep foundation systems. Because concrete piers can extend deep into the ground, they can provide additional stability. For this reason, they are often used to support very large buildings and bridges.
When you are installing a retaining wall (because of the way that retaining walls experience extremely asymmetrical lateral forces, they often require bracing from a series of piers).
When you are repairing foundations that have settled.
Stabilizing a slope (either with or without the use of a retaining wall)
When you are building a structure in an earthquake zone that requires seismic loading. Concrete piers can provide a great deal of stability in the face of earthquakes because of the way that they engage with lateral movement. This obviously makes them additionally attractive in areas such as the Pacific Coast, where fault lines meet coastal soils.

There are, therefore, a number of areas in which concrete piers provide an extremely sound option for a structure. Generally, the larger the structure and the more unstable the surface, the more likely that concrete piers are the best foundation choice.

What are the Costs of Using Concrete Piers?

One of the limitations of using concrete piers is the cost. They can run to be more expensive than a concrete slab, although there are ways of saving money if your budget is tight.

GENERALLY,

for a concrete pier, you’ll likely pay $1.50 to $24 per linear foot, with an average cost of somewhere around $5 per linear foot. There is a great deal of variance in the overall price. For example, an average house that has around 150 linear feet of space is most likely to pay anywhere between $225 and $3,600 for the project.

It is very much recommended that you hire professionals to complete the work. Although you may be tempted to do even a small part of the project yourself, when it comes to foundations, it’s simply not worth it. The long-term cost of a mistake will far outweigh any short-term savings you may make.

A piece of concrete can support 1,500 to 6,500 pounds per square inch. This strength makes it ideal for supporting the weight of large structures. A concrete slab can support a huge amount of weight. However, where concrete can struggle is when force is applied in different directions. Concrete piers are almost exclusively designed because of the way they handle lateral forces. In any situation where lateral forces are likely or possible, a concrete pier is the best foundation. Concrete piers are also extremely adept at rescuing other forms of foundation.

They may be extremely simple in their design, but a concrete pier is one of the most long-lasting ways you can support a structure. There’s a reason why they are used to support skyscrapers and bridges – even those in earthquake zones.