A concrete pier is a vertical concrete support poured or precast to bear a structure’s load at a specific point, commonly used beneath decks, porches, and post-and-pier foundations. It’s typically set into a drilled or dug hole extending below the local frost line for stability.
Some concrete piers are poured in place using cardboard tube forms, while others are precast and simply dropped into a prepared hole, depending on local practice and soil conditions.
What Does a Concrete Pier Involve?
- A drilled or excavated hole below frost depth
- Poured or precast concrete filling the hole
- A bracket or anchor for connecting posts above
- Compacted soil or gravel base beneath it
Why Are Concrete Piers Important?
A concrete pier set below the frost line resists frost heave, the seasonal upward movement that can occur when shallow concrete freezes and thaws with the surrounding soil. Skipping proper depth on a deck or porch pier is a common mistake that leads to uneven, shifting structures within just a few winters, which is why local code typically specifies a minimum pier depth based on regional frost data.
Homeowners building a deck themselves sometimes underestimate this requirement, assuming a shallow pier will be fine for a lightweight structure, only to find the deck heaving and settling unevenly after its first winter. Some regions also require a minimum pier diameter in addition to depth, since a pier that’s too narrow can be prone to buckling under load even if it’s set deep enough to avoid frost heave. Local frost data, available through most building departments, is the standard reference point contractors use to determine the correct minimum pier depth for a given region.
Concrete Pier vs. Foundation Pier
A concrete pier specifically describes a poured or precast concrete support, often used for smaller structures like decks. Foundation pier is the broader category that can also include steel or helical pier systems used to support or repair an entire house foundation.