What is the purpose of underpinning?

Underpinning is used to lower the bearing level of an existing foundation, typically to accommodate an adjacent excavation. We specialize in hand-dug piers, bracket piles, micropiles, jet grouting and other innovative systems.

Schnabel has the expertise to help you determine the solution you need.


Underpinning Construction Contractors

Underpinning is used to transfer the load from an existing structure’s current foundation level to a deeper level in the ground. There are several reasons why this may be required. Often an excavation for a new structure will occur within feet or inches of an existing foundation, and the bottom of the new excavation will be lower than the bottom of the existing foundation. To prevent damage to the existing structure, its foundation is extended to an elevation below the bottom elevation of the proposed excavation using underpinning.

Another use for underpinning is to mitigate settlement of existing foundations. Underpinning construction can be used to transfer the foundation load to a deeper and more competent soil stratum. This same method of load transfer can be used if there is a desire to add additional load to an existing structure in excess of the capacity of the existing foundations.

One of the most accomplished nationwide underpinning contractors, Schnabel has decades of experience in the design and construction of hand-dug piers, bracket piles, micropiles and other systems used to underpin structures. More recently, Schnabel has also used jet grouting and soil mixing for underpinning. Schnabel’s design-build approach to underpinning combines regular monitoring with close communication between our experienced engineers and field staff. This allows us to keep the movements of some very sensitive structures well within acceptable limits.

A premier earth retention contractor, Schnabel can help you achieve your highest goals. To learn more about underpinning construction, contact our office today.

We’re continually focused on protecting our employees and clients from any unnecessary risk.


Schnabel designed and built a complex system of underpinning and excavation support to construct a depressed 2-mile long railroad trench through the center of Reno in Nevada. Schnabel was awarded the Outstanding Project Award by the DFI for its work on this project.

Capitol Crossing

Schnabel designed and installed over 100,000 square feet of excavation support for the Capitol Crossing project in Washington, DC. This project required several innovative solutions from Schnabel including underpinning, soldier piles, lagging, tiebacks, braces, (SASM) walls, micropiles, and tiebacks.”

Schnabel was part of Granite’s design-build team that constructed a depressed 2-mile long railroad trench through the center of Reno that eliminated many at-grade RR crossings. Schnabel installed temporary shoring for the trench excavation and where the trench walls needed to be installed below existing structures, Schnabel constructed permanent hand-excavated reinforced concrete underpinning piers below the groundwater table through boulders up to 8 ft in diameter. Schnabel received Deep Foundation Institute’s Outstanding Project Award for its work on this project.

Claus Ludwig, P.E., RenoRETRAC Project


Schnabel is the sector’s most operationally efficient Geostuctural Design & Construction contractor. We optimize efficiencies by everaging decades of experience and design/build expertise, to innovate processes and approaches that are consistently proven to deliver optimal outcomes for our clients.