A pier foundation supports a structure on a series of isolated vertical supports, called piers, rather than on a continuous footing or slab, typically raising the building above grade. It’s common for structures on sloped sites, in flood-prone areas, or wherever minimizing ground disturbance and excavation matters.
Because each pier is installed independently, this foundation type can adapt more easily to sites where a continuous trench for a footing would be impractical or environmentally disruptive.
What Does a Pier Foundation Involve?
- Individual concrete or masonry piers at regular intervals
- Footings beneath each pier
- Beams spanning between piers to support the floor structure
- Ventilated open space beneath the raised floor
Why Are Pier Foundations Important?
On steep or uneven sites, a pier foundation can adapt to varying ground elevation more easily than a continuous foundation wall would, since each pier can be set independently at the correct height. In flood-prone areas, raising a structure on piers also keeps the living space above expected flood levels, which is a common code requirement in coastal and riverside construction.
This raised, open design also allows floodwater or storm surge to pass beneath the structure rather than against a solid wall, reducing the hydrostatic force the building has to withstand during a major weather event. The specific pier spacing and depth required depends heavily on local soil conditions and the loads involved, which is why a geotechnical evaluation is typically recommended even for smaller pier-supported structures like decks or additions. Because piers are discrete points rather than a continuous element, engineers pay particular attention to how the connecting beams distribute load evenly across every pier in the system.
Pier Foundation vs. Pile Foundation
A pier foundation typically uses shorter, wider supports resting on stable soil near the surface, while a pile foundation drives long, slender supports deep into the ground to reach load-bearing soil or rock far below grade. Piles are used when surface soil alone can’t support the structure.