Piers and footings are terms used to describe parts of the concrete foundation built under a structure to support the weight of the building. When a home, commercial building or deck is constructed, the structure must rest on a concrete foundation to prevent the weight of the building from causing the ground to shift. Piers and footings are regulated by local and state building codes. These codes vary regionally based on existing weather patterns and ground configuration.
Concrete Footings
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A concrete footing is the bottommost part of a building's foundation. Made from poured concrete, and resting on undisturbed ground, the footing forms an upside down "T" at the bottom edge of the concrete wall. The term "footing" can also be used to describe a poured concrete pad at the bottom of a hole that supports the post for a deck. When building a deck that's anchored to a home, the deck posts should rest on a concrete footings to prevent the deck from moving or pulling away from the home, Concrete Network.com advises.
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Concrete Piers
A pier is a concrete columns that's cast atop of a footing and is connected to the footing by steel rebar. The pier, built between the footing and the ground level, usually extends above ground level so wooden posts can be mechanically anchored to the pier. When pouring a footing that will support a pier, rebar is placed into the footing, which extends vertically out of the surface of the footing, according to the BestDeckSite website. When the pier is poured on top of the footing, the rebar connects the two, creating a one-piece foundation structure out of a two-step operation.
Standard Footing Design
A footing is required for piers and foundation walls. As a rule of thumb, for residential buildings, the footing is twice the width of the wall that it supports. This same design is used when the footing supports a pier or a concrete wall. As a result, the footing distributes the weight or load of the wall onto a large surface area of undisturbed earth. Because the footing is wider than the wall or pier resting on top of it, the footing also prevents the pier or foundation from lifting out of the earth.
Typical Pier Configuration
A concrete pier supports the wooden posts used for a deck or pole barn construction. For structures that don't have a continuous foundation wall, a concrete pier carries the load of the post. This pier distributes the load onto the footing that rests on undisturbed soil at the bottom of the footing hole.