Underpinning Contractor

Foundation Underpinning for At-Risk Structures

GeoStabilization International is the underpinning contractor of choice when existing foundations require added capacity, deeper bearing, or stabilization.

For more than 20 years, our design-build teams have delivered foundation underpinning across North America, helping general contractors, DOTs, owners, and developers protect assets, maintain operations, and control schedules and budgets.

With micropiles, targeted grouting, and specialized access methods, we strengthen foundations with low vibration and minimal disruption, even in confined interiors, steep terrain, and remote environments.

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Foundation Underpinning
Underpinning Diagram

Why Choose GSI as Your Underpinning Contractor

  • Turnkey Design-Build Delivery: Our in-house geotechnical engineers and field crews manage every phase, from assessment through installation, ensuring one accountable partner and streamlined execution.
  • Remote and Limited-Access Capability: Compact drill rigs, rope-access teams, and aerial logistics enable safe, efficient work in interior spaces and difficult terrain.
  • Low-Vibration Methods: Drilled and grouted systems protect adjacent or historic structures by minimizing vibration and ground movement.
  • Rapid Mobilization: Our nationwide footprint and specialized fleet allow fast response and compressed construction schedules.
  • Safety and Quality Management: Rigorous procedures, material testing, and documentation meet or exceed industry standards, ensuring precision and reliability.

What Is Underpinning?

Underpinning strengthens existing foundations by transferring load to deeper, more competent soils or bedrock. It is commonly used to:

Repair or stabilize settled or compromised foundations and slabs

Reinforce sinkhole-affected or variable fill areas

Support new stories, basements, or heavier occupancies

Protect structures near deep excavations or dewatering zones

Improve performance where cracking or differential settlement is present

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Our Capabilities

As a trusted underpinning contractor, GSI provides comprehensive solutions tailored to each site condition:

Small-diameter drilled and grouted piles with steel reinforcement provide high compressive and tensile strength, ideal for restricted-access sites.

Steel or concrete systems connect existing foundations to new piles while maintaining operational continuity.

Densifies soils, fills voids, and enhances bearing capacity; complements underpinning for long-term performance.

Adds lateral and uplift resistance for critical infrastructure and essential facilities.

Limited-access underpinning along property lines and near deep excavations.

Rapid stabilization for active settlement, sinkholes, or scour conditions.

Our specialized equipment and logistics enable underpinning in confined interiors, overhead-restricted spaces, steep slopes, and isolated sites, with less excavation and faster mobilization.

How GSI Delivers Foundation Underpinning

  • Assessment and Monitoring – Review subsurface data, map cracks and settlement, define loads, and establish performance targets.

  • Design-Build Engineering – Select pile type, dimensions, and reinforcement; design grouting, casing, and corrosion protection systems.

  • Limited-Access Drilling – Advance piles in staged sequences to maintain stability and minimize disruption.

  • Load Transfer and Integration – Install beams or pile caps to connect to existing foundations; perform proof and load testing as required.
  • Closeout and Guidance – Deliver testing results, as-built documentation, and maintenance recommendations for durable performance.

Project Spotlight:

Tramway Tower Underpinning in Limited-Access Terrain

 

When a tramway manufacturer required tower foundations in an isolated mountain site, conventional methods weren’t feasible. GSI deployed limited-access drill rigs and launched SuperMicropiles, mobilizing equipment by helicopter. The result: engineered capacity, minimal disturbance, and a practical construction plan where standard approaches couldn’t succeed.

The GSI Advantage

 

Certainty in Difficult Ground

Micropiles and grouting perform in variable soils, fill, and rock.

Minimal Disruption

Small rigs, low-vibration drilling, and staged construction protect surrounding operations

Schedule and Cost Control

Design-build delivery streamlines coordination and compresses timelines.

Nationwide Coverage

Local responsiveness supported by a large, experienced field network.

Client Reviews

Reliable Project Support in South Dakota

Cameron, I’m glad you followed up because I don’t do a good job of telling people they did a good job sometimes and I know you’re like me if you hear nothing bad then it must have been OK. From my standpoint, you guys really helped us out by being able to get a crew here quickly which is just what we needed. As for the crew they were fantastic, pretty hands off on my end, didn’t require much of my time and did everything they said they were going to do when they said they were going to do it. Which believe me is very refreshing. So, thank you guys for all your help and I do look forward to an opportunity to work with you again.

Safety-Focused Project Support for Commercial Client in Tennessee

I wanted to take a moment to express gratitude and satisfaction with the job that GSI performed for me.  This work was inside a very congested industrial environment which also had other potential hazards with the presence of alcohol. In addition to confined quarters inside the building we had extreme weather conditions taking place outside the building.  My client was on a critical path timeline and this required GSI to return the week between Christmas and New Year’s. I knew that this was a mandatory week off for GSI but your organization came through, no ifs, ands or buts.

1.) The job superintendent, Ian Turner, handled himself remarkably. He was professional and no matter what the situation he took ownership.

2.) Every person on my job site with GSI had an extraordinary attitude. Case in point: As I was giving a “pep talk” I commented, “some of you guys may be ready to go home”. Emanuel from Georgia, raised his head looked at me and said “no, we wanna finish this job”. Every single person on this project is welcome to work on my projects anytime!

3.) Jarrod Hartshorn was as stated in your company policies willing to communicate 24/7. He answered his phone night or day and if he didn’t in a short while I could expect a phone call.  Jarrod also drove to my project to check on things with me and with the crew working.

4.) One of the best safety programs I have ever witnessed! I enjoy doing “flex and stretch“ with the crew every morning. Thank you!

5.) Hats off to all those volunteers the week after Christmas.

I wish I could remember all names but a special thanks to everyone on my project [including] Preston, Emanuel, Ian, Cole, Cliff, Jarrod, Zach, and the maintenance guy from Kentucky.

Stress-Free Installation Experience in Virginia

Hope all is well, I wanted to reach out and say that I had a great experience working with you all.  Freddy and his whole crew did everything they could to make my job stress free, as well as doing a great/timely/clean installation.  They were all knowledgeable and safety conscious throughout the entire job, and if I ever had a request or felt uneasy they did everything they could to comply with me.

If you have anything else around that you think we could help out with, please contact me at any time.

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Need foundation stabilization or added capacity? Our geotechnical experts respond quickly with design-build solutions that restore structural integrity and minimize disruption.

Request a site assessment or proposal today.

855.579.0536

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