Foundation services
Underpinning and pier installation
How the four pier systems differ, what the evaluation reports leave out, and how to compare bids line by line.
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Written by HyreFoundation Research Desk Primary-source research and fact checking
The short answer
Underpinning moves the weight of a settling foundation down past weak soil onto ground that will hold it. The four systems are push piers, helical piles, pressed concrete pilings and drilled piers.
The right one depends mostly on how heavy your house is and what the soil does, because push piers and pressed pilings use the house itself as the jack that drives them.
Key takeaways
It does not fix heave or a wall pushed inward by soil.
, so a light structure cannot drive them as deep.
, so building weight does not cap their depth. They suit porches, additions and light slabs.
Lifting can crack finishes, masonry and plumbing.
The evaluation reports say soil interaction is outside their scope.
Which underpinning system fits your house?
The four systems are not grades of one product. How each one is driven into the ground decides where it works, more often than price does.
| System | How it works and where it fits |
|---|---|
| Push piers (resistance piers) | Steel tubes pressed down through a bracket on the footing, using the house’s weight as the reaction, until they stop or the house starts to lift. They carry compression only. Best under heavier structures. |
| Helical piles | A screw-shaped plate turned into the ground by machine torque. Capacity is inferred from that torque. Not limited by building weight, and able to resist uplift as well as load. The usual choice for porches, decks, additions and single-story slabs. |
| Pressed concrete pilings | Precast cylinders jacked down one on another, using the house as reaction, holding mainly by skin friction. Common in Texas clay. The trade guideline says refusal depth varies pile to pile and the system will not resist uplift. |
| Drilled or bell-bottom piers | Holes augered, often belled at the base, reinforced and filled with concrete to a depth an engineer sets. They can reach below the soil that swells and shrinks with moisture, and can be reinforced for uplift. |
None of these fixes heave. When soil is swelling, the fix is moisture control, sometimes a barrier or new soil. A pier plan sold for heave means nobody diagnosed it. See why foundations move and repair methods compared.
What do ICC-ES evaluation reports leave out?
Most companies cite an ICC-ES report number. Here is what the reports themselves say they do not cover.
A push pier report says the interaction between the piles and the soil "is outside the scope of this report". It checks steel, brackets and connections.
The same report excludes settlement of the pier itself and whether your existing footing can take the bracket.
Capacities assume 50 years of sacrificial steel. Aggressive soils are excluded: resistivity under 1,000 ohm-cm, pH under 5.5, high organic content, sulfates over 1,000 ppm, landfill and mine waste.
AC358 limits shaft size, helix diameter, spacing, pitch, advance per turn and install speed. Outside those limits, the torque reading no longer proves capacity.
AC358 uses a safety factor of 2, raised to 2.5 where no site-specific geotechnical information exists.
The reports require sealed calculations and drawings approved by the code official. Several also require special inspection during installation.
One report requires the design professional to confirm that lifting will not overstress the foundation or the frame above it.
How does a pier installation run?
Method, pier locations, assumed depth and target result, ideally from an engineer you hired. Permits and any special inspection are arranged against that scope.
Pits are dug to expose the footing at each pier. Outside, that means landscaping and sometimes paving. Inside, it means cutting floors and putting them back later.
Each pier is driven or screwed down to refusal or to a set torque and depth. Ask for the per-pier log of depth and pressure or torque. It is the only proof of what went underground.
Brackets are engaged and the weight moves from the soil to the piers. This is where the system starts working.
A separate decision. Any lift is done in small steps and watched. It is limited by the reaction available. Expect some cracked finishes, and expect an honest contractor to warn you first.
Pits are closed and floors and landscaping restored, if the contract says so. It often does not. Confirm in writing who puts what back.
A post-repair elevation survey, a plumbing re-test if one was done before, and the paperwork: pier log, warranty and as-built pier locations. Keep all of it for resale.
What moves the price
Foundation bids vary more than almost any other trade. The same crack can call for a downspout extension or two dozen piers. The scope sets the price, so compare scopes first. Our pier count estimator gives you the questions that make a pier quote checkable.
| Factor | Why it changes the number |
|---|---|
| Method | Push, helical, pressed and drilled systems use different equipment and crews, and cost very different amounts. |
| Number of piers | Set by the length of foundation affected and the loads on it, not by how many cracks you can see. |
| Depth to bearing | How far down firm soil sits. It varies across one lot and is the line most likely to change mid-job. Get the rate per extra foot in writing. |
| Access | Inside work means cutting and restoring floors. Outside work means digging, landscaping and sometimes removing paving. |
| Soil and site | Expansive clay, fill, slope and water table. Dense granular soil can resist pressed pilings so hard they cannot be driven at all. |
| Plumbing tests | A static test before and after, plus any repair the test finds. This matters most under slabs. |
| Engineering and permits | Assessment, sealed calculations, permit and any special inspection. The smallest lines on the bid, and the ones that control every other line. |
| Putting things back | Filling cracks, rehanging doors, restoring floors, lawn and paving. Often left out, often assumed. |
HyreFoundation publishes no national average price for this work. Depth to bearing, soil, access and method vary enough between two houses on the same street that a single figure would mislead.
Who should write the repair scope?
An engineer you hire should. Pier count, pier locations, assumed depth to bearing and target lift are engineering outputs. If they arrive with the price from the company doing the work, you hold a proposal. There is nothing for a second company to bid against.
What to ask before you sign
Are you bidding against my engineer’s scope or your own assessment?
Which method, how many piers, where, and to what assumed depth?
What is the rate for each extra foot?
What lift is realistic, and what could stop it?
Which ICC-ES report covers this product, and what does it say is out of scope?
Which registered design professional signs the calculations, and are they independent of you?
Is this permitted, and is special inspection required here?
Will I get a per-pier record of depth and torque or pressure?
Is a static test included before and after?
Who restores floors, landscaping and paving?
What does it cover, for how long, and does it transfer to a buyer? See foundation warranties.
The full checklist is on choosing a foundation contractor.
What to have ready
Bring the report and elevation drawing. Everything else comes second.
Your elevation log and dated crack photos.
Age, construction type and any past repair, including work by a company that has since closed.
Any past leaks, especially under a slab.
Trees, drought, irrigation, new paving or digging next door.
Where this goes wrong
A lower number for fewer piers at a shallower depth is a smaller job. It is not a better price.
Recovering height is harder, less certain and riskier than stopping movement. Many engineers recommend stabilizing and accepting the current position.
It promises nothing you can measure, so you cannot enforce it later.
Deeper bearing is the most common change order in this trade. Without a per-foot rate agreed up front, you negotiate with the pits already open.
Lifting a slab over a leaking line can break more of it. The fight over who pays is worse than the repair.
Once the pits are backfilled, the work is hidden for good. The per-pier record of depth and torque or pressure is the only evidence that will ever exist.
In expansive clay, a trade guideline says the gap under a lifted slab should generally stay open, so swelling soil has room. An offer to foam it may be selling you heave.
Get connected
Tell us about the work
Three short steps: the job, your home, and how to reach you. Nothing goes to a foundation company unless you agree.
A straight answer first. Matching is still being built, so this is not an instant quote. If a wall is moving or a door frame has racked out of square this week, call a structural engineer first.
Find a Foundation Professional
Tell us what you are seeing and where you are. We will follow up about connecting you with foundation professionals serving your area.
Questions
How much does underpinning cost?
Can my house be lifted back to level?
How long does foundation repair take?
Do piers fix foundation cracks?
Will my house need underpinning again?
Is there long-term evidence that pier repairs work?
Written and audited by
HyreFoundation Research Desk
Primary-source research and fact checking
We read the model building code, the federal soil and moisture guidance and the insurer position ourselves, and we publish each figure with the document it came from and the date we retrieved it.
Where a number cannot be traced to a primary source, we say so instead of printing it. HyreFoundation does not inspect, engineer or repair foundations. Authorship is organizational: this desk, not a named persona.
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How this desk works
- Primary sources only. Code statements come from the International Residential Code, Chapter 4, as the model code. Soil statements come from USDA and USGS. Insurance statements come from the policy language and the Insurance Information Institute. We open the source rather than cite a blog that cites it.
- The code is a model, and adoption is local. Your jurisdiction adopts an edition and amends it, and foundation chapters are amended more than most because frost depth and soil are local facts. Every code figure says so.
- We hold no job data. We have no dataset of bids, pier counts or invoices, so no page claims an average from one. Calculators show the arithmetic and the inputs they assumed, and label the result as an estimate.
- We do not diagnose your house. A crack guide can tell you which pattern to measure and when to call a structural engineer. It cannot tell you whether your foundation is failing. An engineer on site does that work.
- We do not repair foundations, and we take no payment for placement, ranking or a favorable mention. Nobody buys a position on this site.
Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
Information on this page is general and varies with soil, climate, foundation type, building code, insurance policy and circumstance.
It is not engineering, insurance or legal advice, and no page can tell you whether your house has a structural problem: that needs a licensed professional on site.
HyreFoundation is an independent foundation resource, not a repair contractor or an engineering firm, and does not perform, supervise or warrant foundation work.