Quick answer
Foundation underpinning is the process of adding remedial supporting elements, such as piers or piles, under an existing foundation so the building rests on deeper or stronger soil than the soil that settled.
It is used to stop further downward movement, to raise a settled building, or to protect it during nearby digging. Method, count and depth depend on loads, soil and the foundation itself, and are set by an engineer.
Quick facts
The key facts about Foundation Underpinning, with sources:
- What it does
- Adds supporting elements under an existing foundation 1
- Stabilization
- Underpinning to limit future downward movement, with or without raising 1
- Elevation adjustment
- Raising or lowering a foundation to a new position 1
- Other use
- Supporting a building next to a deep excavation 2
- Who designs it
- A licensed engineer in states that regulate it, such as North Carolina 6
- Price
- Not quoted here; see the cost drivers section
Key takeaways
- Underpinning means putting new support under a foundation that already exists.
- It covers several methods, from steel piers to precast concrete segments to drilled concrete piers.
- Stabilizing a foundation and lifting it are different goals, and a plan can do one or both 1.
- Underpinning does not remove the cause of movement, such as water, roots or fill, and it cannot promise that movement will not return.
- Method choice, count, depth and layout are engineering decisions that depend on loads, soil and the foundation’s ability to span.
What underpinning means for an existing house
General information, not a diagnosis of your house. The Foundation Performance Association defines foundation underpinning as the process of adding remedial supporting elements, such as piles, under an existing foundation system 1. In a house, that usually means a bracket on the footing or slab, connected to a pier that reaches a deeper layer.
The idea is old. A New York patent from 1896 described driving tubular steel columns to bedrock or firm soil with hydraulic jacks that pushed against the weight of the building, and said the method allowed raising or lowering of structures 2.
Modern systems are manufactured products, but the logic of reaching past weak soil is the same.
Underpinning is a category, not one product. The methods are covered on their own pages: push piers, helical piers, pressed concrete piers and drilled piers.
Two cutaways of a footing. Left: a steel push pier pushed down through a bracket under the footing to firm soil. Right: a helical pier with spiral plates screwed down through a bracket under the footing. Both go below weak upper soil.
Illustrative drawing, not to scale and not a design. It shows two kinds of pier carrying a footing down past weak soil. Depth, spacing and loads come from an engineer’s design for each building.
Underpinning is not slab lifting
Underpinning adds support under footings or slabs. Mudjacking and foam lifting fill voids under a slab and raise it. They are different tools for different problems, and one does not replace the other 8.
Foundation stabilization: stabilizing versus lifting
Foundation stabilization is the term many repair quotes use for underpinning. The Foundation Performance Association defines it narrowly: underpinning the foundation to help minimize future downward movement, without regard for elevation adjustment 1. In other words, stabilization is about holding the foundation where it is.
Foundation elevation adjustment is the process of raising or lowering the foundation to a new vertical position, in an effort to reduce distress, deflection or tilt 1. Lifting a building is an elevation adjustment, and it is a separate step from stabilizing.
The two goals often travel together, but not always. A plan may only stabilize. A plan may also lift. A good quote says which, and it says why.
Lifting adds stress to finishes, pipes and the structure, and the foundation’s ability to handle that is part of the engineering check.
The same source says a geotechnical investigation and structural analysis are of value when raising a foundation above the potential vertical rise 1.
No method fits every house
Underpinning design depends on loads, soil, installation and engineering assessment. A method that suits one house can be wrong for the next. Do not choose a method from a brochure, a photo or a sales call.
How underpinning works, in six steps
- The cause is evaluated. A licensed engineer looks at the building, the soil and the water. North Carolina’s board says a statement that a foundation has failed, or that structural repair is needed, should come from a licensed engineer who evaluated it 6.
- Soil data is gathered. Borings or probes locate a layer firm enough to carry load and find barriers such as fill or boulders 2.
- A layout is designed. The engineer sets the pier type, locations and the goal. Wall and footing must be able to span between support points 2.
- Brackets are attached and elements installed. Piers are pushed, screwed or built down to the bearing layer 24.
- Load is transferred. The building weight moves from the old support to the new elements. If the plan includes lifting, it is done here.
- Records are kept. Installation logs, test records and before-and-after elevations show what was done 1.
Common underpinning methods and how each one works
| Method | How it works | Fits when | Limits |
|---|---|---|---|
| Push piers | Steel pipe pressed down against the structure’s weight 3 | A dense layer lies within reach 2 | Needs a firm layer; capacity is mostly at the tip 3 |
| Helical piers | Shaft with spiral plates turned in by a machine 4 | Access is tight or vibration must be avoided 2 | Rock and shallow bedrock; corrosion 4 |
| Pressed concrete piers | Precast segments pressed in one by one 1 | Clay soils where driving resistance is small 1 | Dense granular soil resists driving; limited uplift and bending resistance 1 |
| Drilled piers | Hole drilled and filled with reinforced concrete, sometimes with a bell 7 | Support below a moisture active zone is needed 5 | Water, sand and caving soil complicate drilling 5 |
| Excavated footings and walls | Excavating and rebuilding footings, walls or beams | Soil conditions allow it 2 | Less desirable in fill, compressible, organic or expansive soils 2 |
Example: what “underpinning” can mean in a quote
The same word covers different scopes. These definitions come from Foundation Performance Association guidelines and a manufacturer manual, so they show the range, not one plan 12.
| Scope in a quote | What it means | Question to ask |
|---|---|---|
| Partial underpinning | Piers under only a portion of the structure, such as one side | What is unsupported, and why is that acceptable? |
| Complete underpinning | Piers under the entire exterior and interior of the structure; may be used to lift above potential vertical rise | Is lifting included, and what is the target elevation? |
| Stabilization only | Underpinning to limit future downward movement without raising | What movement will be monitored afterward? |
| Elevation adjustment | Raising or lowering the foundation to a new position | How much, how fast, and who checks the structure? |
| Shoring for adjacent digging | Underpinning a neighbor’s or addition’s adjacent foundation during deep excavation | Who is responsible if the existing building moves? |
- EvaluateCause and condition
- Investigate soilBorings or probes
- DesignMethod, layout, goal
- InstallWith records
- MonitorElevations over time
A general sequence from engineering guidance, not a schedule for any house. Source: [6] [2] [1]
Each row needs a drawing, a layout and a responsible party, not just a line item.
Where underpinning is used
The most common home case is a footing or slab that has settled because the soil under it was soft, wet, filled or shrinking. Manufacturers say fill areas, compressible soils, organics and expansive soils are common underlying causes of remedial repairs 2.
A second case is protecting a building during nearby digging. The manufacturer’s manual describes using underpinning together with shoring when an addition or new building needs excavation much deeper than the existing footing 2. If a neighbor plans a deep excavation, that is a reason to ask an engineer.
Underpinning also appears in new construction repairs, on retaining structures and under columns. The foundation types guide shows where each kind of foundation can take brackets.
What underpinning offers and what it costs you
What it can offer
What underpinning cannot do
Underpinning cannot change the weather, the water or the roots that moved the soil. The North Carolina engineering board notes there may be reasons for a failure that should be addressed, which is why analysis comes first 6. After underpinning, soil between and beside the supports can still shrink, swell or wash out.
It also cannot promise that movement will stop. Foundation Performance Association writers say piles that do not reach stable soil may not resist movement caused by swelling and shrinking soil in the active zone, and that some pile types will not resist uplift if soil in contact with the foundation swells 1.
Stabilizing limits downward movement. It is not a guarantee against all movement.
Finally, underpinning is not a fix for a bowing wall or a cracked wall. Those need their own evaluation. See the foundation cracks guide.
What drives the cost of underpinning
We do not give prices. A reliable number needs dated local quotes for a defined scope. Here is what moves the figure: the method, the number of supports, how deep each must go, whether the plan stabilizes only or also lifts, and whether the job is partial or complete.
Access matters, and so do interior floor breakout, utility locates, groundwater control and restoring finishes. Engineering design, testing, permits and monitoring add cost, as do drainage and plumbing repairs that treat the cause.
Use the repair cost guide, the cost calculator and the pier count estimator to see how the parts add up. They are teaching aids and do not replace a design.
How to run an underpinning project as a homeowner
- Photograph and date what you see. Do not dig, jack or enter a crawl space with standing water. Use the crack identification tool to describe what you see.
- Hire a licensed structural engineer to evaluate. Our engineer guide and engineer or contractor tool help you decide.
- Ask for borings or probes if the engineer calls for them.
- Get a written design, then price it with more than one contractor. See choosing a contractor.
- Check licenses with your state boards, not with the company.
- Keep records, and log elevations afterward with the elevation log.
Looking after the foundation after underpinning
- Keep gutters and downspouts clear, and soil sloping away from the wall. See drainage and grading.
- Keep the installer’s drawings, logs and warranty. See warranties.
- Look at doors, windows and cracks every few months and photograph them with dates.
- Ask the engineer whether elevation readings should continue and for how long.
- Fix plumbing leaks promptly, since water changes the soil.
Risks, unknowns and when to call an engineer
- The cause is not found, so movement continues next to the new supports.
- Supports are too far apart for the wall or footing to span 2.
- Piers stop early on fill, boulders or hard layers 2.
- Steel corrodes in aggressive soil, so protection should be specified 4.
- Lifting cracks finishes or damages pipes if done too fast or unevenly.
- Design is left to the product maker with no engineer in charge 6.
Call a licensed structural engineer when
Movement is large, widening or changing; walls are bowing or displaced; doors and windows stick together with new cracks; a corner is separating; or you have any safety doubt. Never dig next to a foundation or jack a house yourself.
Codes, permits and who may design underpinning
Pier systems are deep foundation elements, and the International Building Code lets a building official approve deep foundation types it does not name, on acceptable test data and calculations. Foundation Performance Association writers use that provision to explain how precast segmented piles are permitted 1. Check which code edition and amendments your jurisdiction adopted.
State rules on who designs repairs vary. North Carolina’s board says the analysis, recommendation and design of a repair must be done by a licensed engineer, including the number and location of piers, and that repair companies cannot leave design to a product maker 6. Check your own state board before signing.
A product certification or a company badge is not a license. Verify with the issuing board. See how we vet for what we do and do not check.
Underpinning compared with other foundation fixes
| Fix | What it changes | What it does not do |
|---|---|---|
| Underpinning | Adds support under an existing foundation 1 | Remove the cause of movement |
| Mudjacking | Fills voids under a slab with grout to lift it 8 | Add deep support under footings |
| Foam slab lifting | Injects expanding foam under a slab 9 | Carry a footing down to firm soil |
| Drainage and grading | Changes where water goes near the wall 10 | Raise a settled footing |
| Replacing the foundation | Builds a new foundation | Fix the cause of the soil problem by itself |
Underpinning myths
- Myth Underpinning always lifts the house.
- Reality Stabilizing and lifting are separate goals; a plan can do either or both 1.
- Myth Every cracked foundation needs underpinning.
- Reality No source says that. A crack is a clue, and an engineer must find the cause first 6.
- Myth A bigger pier count is a better repair.
- Reality Count comes from loads and the foundation’s ability to span, not from a rule of thumb 2.
- Myth The manufacturer designs the repair.
- Reality Regulators say repair companies cannot leave design to the product maker 6.
- Myth Once underpinned, the house never moves again.
- Reality Soil outside the supports can still change, and no source promises otherwise.
Regional soil and why underpinning varies by state
Expansive clay is prevalent in Texas and the Gulf Coast, the Appalachian states, the Southwest and the Great Plains, according to the Federal Highway Administration’s drilled shaft manual 7.
In those regions, designers often look for support below the moisture active zone 5. In cold regions, frost depth and frost-susceptible soils change footing behavior. State licensing rules on who may design a repair also differ 6.
Deciding whether underpinning is the right category
Underpinning is the right category when a footing has moved down, the cause is understood and deeper support is feasible. It is the wrong category when the problem is a void under a slab, a drainage fault or a wall pushed by water pressure, which have their own fixes.
Use the guide below to prepare. For the wider menu, see repair methods, foundation repair and the repair method tool.
- If A footing has settled and a cause is known
- Then Ask the engineer whether underpinning suits the soil and loads
- If The slab is hollow or low but the footings are stable
- Then Ask about slab lifting instead 8
- If A wall is bowing
- Then Ask about wall repair, not piers
- If A neighbor will dig deep next door
- Then Ask an engineer about protecting your foundation 2
Engineer first, contractor second
The engineer decides whether to underpin and how. The contractor installs it. If one company does both, ask who is accountable for the design.
Questions about Foundation Underpinning
What is foundation underpinning?
Foundation underpinning is adding remedial supporting elements, such as piers or piles, under an existing foundation so the building rests on deeper or stronger soil. The Foundation Performance Association defines it that way. It can stabilize a foundation, raise it, or protect it during nearby excavation.
What is foundation stabilization?
Foundation stabilization is underpinning the foundation to help minimize future downward movement, without regard for raising it. It is a different goal from elevation adjustment, which raises or lowers the foundation to a new position. A repair plan can include one or both, and your quote should say which.
Is underpinning the same as lifting a house?
No. Underpinning adds support. Lifting, called elevation adjustment, is a separate step that some plans add after the supports are in place. Not every underpinning job lifts the structure, and lifting adds stress that an engineer should plan for.
What are the main types of underpinning?
For houses, the common types are steel push piers, helical piers, precast concrete piers pressed in segments and drilled concrete piers. Excavated footings and walls are another category. Each fits different soils and loads, and each has limits. An engineer chooses the method.
Does underpinning fix cracks?
It may help stop the movement that opened them, but it does not repair the crack. Cracks are clues, not diagnoses. An engineer must find the cause first. Crack repair, if needed, is a separate step. Our crack guide explains what to record.
Will underpinning stop my foundation from moving?
No source promises that. Underpinning limits downward movement of the supported parts, but soil between and beside supports can still change, and some pile types do not resist uplift. Ask the engineer what the plan does and does not address.
Do I need an engineer for underpinning?
In some states, yes. North Carolina’s engineering board says a licensed engineer must make the analysis and design of repairs, including pier number and location. Rules vary by state, so check yours. An independent engineer can also compare contractor plans.
Can a neighbor’s digging damage my foundation?
It can. A manufacturer’s manual notes that deep excavation next to an existing building can need underpinning and shoring to prevent movement of the adjacent footing. If a neighbor plans deep work, ask a structural engineer whether your foundation needs protection.
How much does underpinning cost?
We do not publish prices. The drivers are the method, the number and depth of supports, whether the job lifts, access, engineering, permits and finish repairs. Our cost guide and calculator show how quotes are built so you can compare scopes line by line.
Sources
- Foundation Performance Association, FPA-SC-08-1: Design, Manufacture, and Installation Guidelines of Precast Concrete Segmented Piles for Foundation Underpinning (2014), definitions and design considerations, retrieved .
- Hubbell Power Systems (CHANCE), Technical Design Manual, Edition 3 (2014): introduction, feasibility and underpinning/shoring sections. Manufacturer document, retrieved .
- Hubbell Power Systems, Foundation Solutions blog: Push Piers, Frictional or End Bearing? Manufacturer document, retrieved .
- Iowa State University Bridge Engineering Center and InTrans, Helical Pile Foundation Guide for Bridge Structures (October 2023), retrieved .
- Foundation Performance Association, FPA-SC-01-0: Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils (2004), retrieved .
- North Carolina Board of Examiners for Engineers and Surveyors, Foundation Repair Guidelines (revised 10/22/2024), retrieved .
- Federal Highway Administration, Drilled Shafts: Construction Procedures and LRFD Design Methods, GEC 10, FHWA-NHI-10-016 (May 2010), retrieved .
- Federal Highway Administration, Concrete Pavement Preservation Guide, 2nd ed., FHWA-HIF-14-014 (2014), Chapter 4: Slab Stabilization and Slab Jacking, retrieved .
- Oregon Department of Transportation, Injected Polyurethane Slab Jacking, FHWA-OR-RD-02-19 (June 2002), retrieved .
- Kansas State University Research and Extension, Dry Basements and Crawl Spaces, MF2809 (April 2008), retrieved .
Expert review
Written by the HyreFoundation Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Definitions of underpinning, stabilization and elevation adjustment, and the limits of piles, come from a Foundation Performance Association peer-reviewed guideline.
Methods, history, feasibility and shoring notes come from a manufacturer technical manual, labeled as a manufacturer document, plus Iowa State University, FHWA and Foundation Performance Association references. Licensing statements come from the North Carolina engineering board. No prices, depths, spacing or loads are given. Rules checked 2026-10-14. General information, not engineering advice.
Suggest a correction. We fix errors and say what changed.