Structural Engineering · Engineering Glossary
A drilled pier (also called a caisson or drilled shaft) is a deep foundation element formed by drilling a cylindrical hole into the ground, placing a reinforcing cage, and filling with concrete. Piers transfer structural loads through weak soils to deeper, competent bearing strata or through skin friction along the shaft.
Drilled piers are used when competent bearing material is too deep for spread footings to be economical, when the soil has high expansion potential that would cause damage to shallow foundations, or when extremely heavy column loads require deep load transfer. Pier diameter typically ranges from 12 inches to several feet, and depth can exceed 100 feet in challenging soil conditions. The geotechnical engineer specifies the required tip elevation, design skin friction, and end bearing capacity. Structural engineers size the reinforcing cage and design the pile cap connecting the pier to the structure above. Apex Grid coordinates pier design with the geotechnical report findings on every deep foundation project.
Apex Grid Engineering maintains this glossary as a resource for architects, contractors, developers, and property owners who encounter unfamiliar engineering terminology on their projects.
View All Engineering TermsApex Grid's licensed PEs provide structural engineering services across multiple jurisdictions — with fast quote turnaround and permit-ready documents.
Request a Proposal