What Is Foundation Underpinning?
Foundation underpinning is the correct technical term for any repair that strengthens or deepens a foundation by transferring its load to more capable soil or rock below the original footing depth. It is the right solution when a foundation is settling because the soil beneath it has compressed, washed away, dried and shrunk, or was never properly compacted in the first place. If your home has sticking doors, diagonal cracks running from the corners of windows and door frames, floors that slope or feel uneven, or visible gaps between walls and ceilings, your foundation may be settling and underpinning may be the recommended fix. APS Foundation Repair and Waterproofing has been underpinning Alabama foundations since 1977, working with homeowners and commercial property owners across Birmingham, Huntsville, Mobile, and Columbus, GA. We assess the cause of settlement before recommending any repair, because underpinning stops future movement but cannot undo damage from a cause that has not been corrected, like an active plumbing leak, uncontrolled surface water, or unresolved drainage problems.
How Foundation Underpinning Works
Underpinning works by installing structural elements, piers, beneath the existing foundation footing. These piers are advanced deep into the ground by hydraulic pressure or rotational force, past the failed surface soils and into stable native soil or rock. Once at bearing depth, the load of the foundation and everything above it is transferred from the failing soil to the piers. The transfer is permanent and mechanical: steel brackets lock the footing to the pier, and the weight of the structure keeps the connection secure. Most underpinning methods also allow for some recovery of the foundation's original elevation through a controlled lifting sequence performed after all piers are installed.
“The most important thing we do before any underpinning job is find out why the foundation settled in the first place. Install piers without fixing a drainage problem or a plumbing leak, and you are putting a bandage on a wound that keeps bleeding. The repair has to address the cause, not just the symptom.”
How APS Installs Foundation Underpinning
- 1
Cause Identification and Inspection
APS begins every underpinning assessment by identifying the cause of settlement, not just the symptoms. We inspect for drainage problems, plumbing issues, soil type, tree root impact, and historical site information before recommending any repair.
- 2
Underpinning Method Selection
Based on soil conditions, structure type, access, and load requirements, APS recommends the appropriate pier system: steel push piers for deep bearing in most conditions, helical piers for lighter loads or torque-confirmed bearing, concrete piers as an alternative in specific soil profiles, or micro piers for limited-access locations.
- 3
Footing Exposure at Pier Locations
Foundation footings are exposed by excavation at each pier location. Excavation depth and method depend on footing depth and site access.
- 4
Pier Installation to Bearing Depth
Piers are installed at each location and advanced to confirmed bearing depth. All pier installations are pressure- or torque-verified, APS does not install piers to a preset depth without bearing confirmation.
- 5
Foundation Lifting and Load Transfer
All piers are connected to the foundation via steel brackets. Hydraulic jacks simultaneously lift the foundation to the target elevation, and then load is permanently transferred to the pier system.
- 6
Drainage and Contributing Cause Corrections
Any drainage improvements, downspout extensions, or other contributing-cause corrections identified during assessment are completed. Excavations are backfilled, and the work area is restored.
What Foundation Underpinning Costs and What Is Covered
Cost Range
$5,000 to $30,000+ depending on scope; free assessment
Warranty
APS in-house workmanship warranty plus manufacturer warranties on all pier components; both transferable to subsequent homeowners
Frequently Asked Questions
How do I know if my foundation needs underpinning or just crack repair?
Crack repair alone addresses a symptom, not the cause. If the cracks are caused by foundation settlement, filling them without underpinning will result in the cracks reopening as settlement continues. APS evaluates whether cracks are active settlement cracks or historical cracks in a stable foundation, and recommends underpinning only when active settlement is confirmed.
Can underpinning level my floors completely?
Underpinning stops future settlement and can recover some of the original floor elevation. Full recovery to the original level is not always possible, it depends on the structure's flexibility, the extent of settlement, and how long the settlement has been occurring. APS sets realistic expectations about leveling outcomes during the assessment.
How many piers will my foundation need?
Pier count depends on the settled area, foundation type, structural load, and pier spacing required by the soil conditions. A typical residential underpinning project involves anywhere from four to twenty or more piers. The assessment and written estimate will specify exact quantities and locations.
What soil conditions in Alabama make underpinning necessary?
Alabama has several soil types that are prone to causing foundation settlement. Expansive Piedmont clays in the Birmingham and central Alabama area shrink and swell with moisture changes. Coastal Plain sediments in and around Mobile can be loose and compressible. Fill soils on leveled lots throughout all markets are frequent culprits. In Huntsville, karst limestone terrain presents additional complexity. APS is familiar with all of these conditions.
Does underpinning affect my homeowner's insurance or my ability to sell the home?
A properly completed and warrantied foundation repair should not negatively affect your ability to sell your home, and in many cases a transferable warranty is viewed positively by buyers and their lenders. We recommend consulting your insurance carrier about any disclosure requirements in your specific policy.