Quick answer
Helical piers are steel shafts fitted with one or more spiral plates that are rotated into the ground until they reach a layer able to carry the load, then connected to a foundation by a bracket so the structure rests on that deeper soil.
Installers watch the torque needed to turn the shaft, because it is related to how strong the soil is. The same piers are used for new construction and for repairs of settling buildings. A licensed engineer decides whether they suit a given house.
Quick facts
The key facts about Helical Piers, with sources:
- Main parts
- Lead section with helix plates, plain extension sections, a bracket to the foundation 1
- Installed by
- Rotating with a hydraulic torque motor while pushing down 1
- Evaluation criteria
- ICC-ES AC358 covers helical pile systems and devices 1
Key takeaways
- A helical pier is a steel shaft with spiral plates that is turned into the ground like a big screw.
- The plates pass load into firmer soil below the layer that moved, so the foundation sits on deeper support 1.
- Installers read torque during installation and relate it to capacity, but the method has stated limits 1.
- They work with small equipment, little vibration and no spoil, which helps on tight sites 1.
- Rock, hard layers and corrosive soils change the plan, and none of this replaces an engineer’s design.
What a helical pier is, in plain terms
General information, not a diagnosis of your house. Iowa State’s helical pile guide defines the pile as a steel pile with one or more helical plates, torqued into the soil until the lead section sits in a layer that can take the structural loads 1.
A foundation can hang from it or sit on it through a bracket.
The same device is known as a screw pile, helical pile or screw anchor.
Foundation Performance Association writers describe the helix as a plate formed into one pitch of a screw thread, which is why the pier can be driven by turning it 3.
Pier and pile are often used interchangeably, and the steel is the same idea.
The helical pier replaces support the upper soil used to give. If you want the broader picture of adding support under a settled footing, read foundation underpinning. For a side-by-side with the other main steel option, see push piers vs. helical 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 a screw-type pier and a pushed pier carrying a footing past weak soil. Plate size, shaft size, depth and spacing come from an engineer’s design.
How a helical pier is turned into the ground
The Iowa State guide describes the field procedure for helical piles. A residential repair uses the same logic at a smaller scale.
- Position the lead section. The lead section, the first piece with helix plates, is attached to a hydraulic torque motor and set at its location. Plumbness is checked 1.
- Apply down force and rotate. The machine pushes down on the shaft, called crowd, while turning it. Each turn advances the pile about one helix pitch 1.
- Add extensions. When the lead section is in, an extension without plates is bolted on and turning continues. This repeats until the planned depth and strength are reached 1.
- Read the torque. A torque indicator records the effort as the shaft turns. Dense soil takes more torque than soft soil 2.
- Stop on criteria. The installer stops when the plan’s torque and depth conditions are met, then records the numbers.
- Attach to the foundation. For repairs, brackets connect the pier to the existing footing so it can stabilize the structure or lift it back toward its original position 2.
No method fits every house
Whether a helical pier suits a house depends on its loads, the soil layers, the condition of the footing, corrosion risk and access. That judgment belongs to a licensed engineer. This page explains how the method works; it does not select it for you.
Helical pier parts and shaft shapes
| Part or choice | What it does | Notes |
|---|---|---|
| Lead section | First piece in; carries one or more helix plates 1 | The plates transfer axial load to the bearing layer by bearing 1 |
| Extension section | Plain shaft added to reach depth 1 | Joined with coupling bolts 1 |
| Square solid shaft | One of the two most typical shaft shapes 1 | Can leave a gap around the shaft as it turns, which matters in expansive soil 3 |
| Round hollow shaft | A pipe shaft has a greater section modulus and larger lateral dimensions 1 | That increases resistance to lateral deflection in soil 1 |
| Grouted shaft | Cement grout placed around the shaft 1 | Adds capacity and corrosion protection when specified 1 |
| Foundation bracket | Connects the pier to the footing 2 | Brackets and shafts are evaluated together under ICC-ES AC358 1 |
Example: how installation torque becomes a capacity estimate
The torque example below is the relationship the sources describe, written out in words and symbols. We give no numeric values, because they differ by manufacturer, shaft and soil.
| Step | What the source says | Source |
|---|---|---|
| 1. Measure | Torque is recorded as the pile advances into the soil | 1 |
| 2. Relate to soil | The torque is indicative of soil consistency and strength | 1 |
| 3. Convert | Ultimate capacity is estimated as a torque factor times the final torque, written Pu = Kt times T | 1 |
| 4. Apply a margin | The allowable load is the ultimate value divided by a factor of safety set by the designer | 2 |
| 5. Check the limits | The method does not apply when the pile ends on bedrock or other hard material, or when the top helix is too shallow | 1 |
Ultimate capacity = Kt × final installation torque
Kt- An empirical factor from the manufacturer’s testing, which varies by shaft
T- Final installation torque, read from the torque indicator
A designer applies a factor of safety to get an allowable load. The relationship has limits near rock and at shallow depth 1.
In the maker’s account, installation torque correlation was developed in the 1960s and works the way a wood screw is harder to turn into oak than pine 2. For the method to work, torque must be measured, which is why torque indicators are part of the equipment 2.
Where helical piers are used in buildings and repairs
The Iowa State guide lists foundation underpinning among the uses of helical piles, along with light and heavy commercial construction, towers, tie-downs and slope tiebacks 1. The manufacturer says they can supplement or replace foundations distressed by differential settlement, cracking or heaving 2.
They are often chosen where machines cannot reach. The manufacturer notes they can go in using portable equipment in confined interior spaces, with no vibration, so a building can keep operating 2.
Foundation Performance Association writers add that they can be installed in low headroom and limited access areas, with little disturbance to the site 3.
Ground matters too. Foundation Performance Association’s design options paper says helical piers can be extended deep below the moisture active zone of expansive soils, because shaft extensions are easy to add, and that the small shaft surface limits uplift or drag-down from soil movement 3. The expansive clay soil page explains that zone.
What helical piers do well and where they struggle
Strengths in the technical sources
- Fast installation with smaller equipment and little ground preparation 1.
- Little vibration and noise, and no spoil to remove 1.
- Capacity can be estimated from the recorded torque as soon as installation ends, within the method’s limits 1.
- Loads can be applied right after installation 3.
- Extensions can reach deeper layers when the first depth is not enough 3.
Limits and trade-offs
- Final length is often only estimated when work is bid 1.
- Rocky sites or shallow bedrock are not ideal 1.
- Steel can corrode, so galvanizing, coatings or extra steel thickness may be needed 13.
- Vertical piers give little resistance to sideways loads because the shaft is slim 3.
- In very soft soils, a slim shaft may need extra support to prevent buckling under large loads 3.
What helical piers cannot do
A helical pier supports the part of the foundation it is attached to. It does not dry out the soil, fix a leaking pipe or repair a cracked footing.
If the cause of movement is not addressed, soil near the piers can keep changing.
Engineers separate stabilizing, which aims to help minimize future downward movement, from raising the foundation, and neither can promise that movement will stop 4.
The torque method has limits. The Iowa State guide says it does not apply when piles end on bedrock or other hard material, or when the top helix is less than a set multiple of the helix diameter below the surface. In those cases load tests or limit state calculations are used instead 1.
Foundation Performance Association writers also note that square shafts can leave a gap around the shaft as they turn, which could let water travel down and wet dry expansive soil, and could speed corrosion 3. These are design points for an engineer, not reasons to rule the method out.
What drives the price of a helical pier job
We do not quote prices. G-COST requires dated, sourced quotes, and a number built from a national average would mislead. What moves the price is better explained.
The main drivers are pier count, shaft size and the number of plates, the depth needed to reach the bearing layer, and whether the job stabilizes or also lifts.
Because final length is often only estimated at bid, the contract should say how extra depth is handled 1. Corrosion protection, grouting, engineering fees, permits, access, interior breakout and finish repairs all add cost.
See the repair cost guide for how quotes are built, the cost calculator for a planning range and the pier count estimator for why counts differ between bids.
What a helical pier project usually looks like
- Evaluation by a licensed engineer. North Carolina’s engineering board says a statement that a foundation has failed, or needs structural repair, should come from an engineer who evaluated it 7.
- Soil information. A soils report gives the data for helical pile design. Unknown conditions do not rule piers out, but they add uncertainty to the design 1.
- A written design. It should name pier locations, torque criteria, who approves changes and what happens if refusal occurs.
- Permit and utility locates, where required by your jurisdiction.
- Installation with records. Torque logs and depths should be kept for each pier.
- Follow-up. Record elevations. The elevation log is a simple way to do it.
Caring for the site after helical piers are in
Steel piers need little upkeep, but the soil and water around them still do.
- Keep water away from the wall. Start with gutters and downspouts; see drainage and grading.
- Keep a copy of the torque log, pier map and any corrosion protection details.
- Look at the same doors, windows and cracks every few months and photograph them with dates.
- Ask the engineer if elevations should be monitored and when to repeat them.
- Keep the warranty and read what it excludes. See warranties.
Risks and signs to take seriously
- Corrosion in disturbed, wet or organic soil. Iowa State notes oxygen-rich disturbed soil can raise corrosion rates and that organic material can speed it up 1.
- Refusal on rock or hard layers, which stops the pile above the planned depth 1.
- Buckling of the slim shaft in very soft soil under high load 3.
- Weak footings or walls that must span between piers 2.
- Contact between steel piles and reinforcing steel, which can raise corrosion 1.
When to involve a structural engineer
Call a licensed structural engineer when cracks widen or change, walls bow or shift, doors and windows stick along with new cracks, or any part of the structure feels unsafe. Never dig beside a footing or try to jack a house yourself.
Evaluation criteria, codes and licensing
ICC-ES publishes Acceptance Criteria for Helical Pile Systems and Devices, called AC358. The Iowa State guide names it as the evaluation route for the products 1.
The manufacturer says certain helical pile types and brackets were evaluated per AC358 2. An evaluation report is a product document. It is not a design for your house.
Model codes treat piers as deep foundations, and each jurisdiction adopts its own code edition and amendments. Check what your building department adopted.
Licensing differs by state. North Carolina’s board says repair companies cannot leave design to the product maker and that an engineer must account for actual field conditions 7. A manufacturer’s installer certification is not a state license. Verify each license with the issuing board, and read our vetting page.
Helical piers next to other deep support
| Method | Installed by | Load passes to soil by | Key limit |
|---|---|---|---|
| Helical piers | Rotating a plated shaft into the ground 1 | Bearing on helix plates 3 | Hard rock and shallow bedrock 1 |
| Push piers | Pressing steel pipe against the building’s weight 5 | End bearing at the tip 5 | Needs a firm layer within reach 2 |
| Drilled piers | Drilling a hole and placing concrete 6 | End bearing and side resistance 6 | Caving or wet ground needs casing or slurry 6 |
| Pressed concrete piers | Pressing precast segments one by one 4 | Mainly skin friction 4 | Dense granular soil resists driving 4 |
Helical pier myths
- Myth Helical piers are always the best option.
- Reality No method is. Iowa State lists rocky sites and uncertain final length as disadvantages 1.
- Myth Torque alone proves the pier is safe.
- Reality Torque is one indicator. The method has stated limits, and designers add safety factors 12.
- Myth Steel does not corrode underground.
- Reality Corrosion protection is typical because soil conditions can attack steel 1.
- Myth Helical piers can resist any sideways load.
- Reality Vertical piers with slim shafts give little lateral resistance; tubular shafts and angled piers are used where needed 31.
- Myth Once installed, the house cannot move.
- Reality Soil beside the piers can still change, and the piers do not remove its cause.
Regional ground that affects pier choice
Expansive soils are common in Texas and along the Gulf Coast, in the Appalachian states, the Southwest and the Great Plains, per the Federal Highway Administration’s drilled shaft manual 6.
In those regions, designers often want support below the moisture active zone, which helical extensions can reach 3. Where frost is the driver, frost depth and frost-susceptible soils matter more. High water tables add a corrosion and installation factor. The answer changes by region.
Deciding whether helical piers belong on the shortlist
Helical piers are worth a look when access is tight, the site cannot take vibration, the bearing layer is deeper than other methods easily reach, or rock is not expected near the surface. They are less clear where shallow bedrock, obstructions or very corrosive soils are likely.
Take the guide below to an engineer. For the full menu, use the repair methods guide, the repair method tool and foundation repair.
- If Access is tight or vibration is a concern
- Then Ask whether helical piers suit the soil and loads 2
- If Bedrock may be shallow
- Then Ask how refusal will be handled and who approves changes 1
- If Soil is wet, organic or filled
- Then Ask about corrosion protection and coatings 1
- If The contract lists pier price but not depth rules
- Then Ask how extra depth is charged, because final length is often estimated 1
Engineer first
Ask a licensed structural engineer to evaluate the foundation and write the repair design, then price that design with contractors. Our engineer or contractor tool helps you decide whom to call first.
Questions about Helical Piers
What is a helical pier?
A helical pier is a steel shaft with one or more spiral plates that is turned into the ground until it reaches soil able to carry the load. A bracket then connects it to the foundation. The plates pass load into the soil by bearing. It is also called a screw pile or helical pile.
How do helical piers work?
A hydraulic motor rotates the shaft while pushing down. Each turn advances the pile about one plate pitch. Extension sections are added until the planned depth and strength are reached. Installers record the torque, which relates to soil strength, and the plates then carry load by bearing on the soil.
What is the difference between helical piers and helical piles?
The steel is the same idea, and the words are often used interchangeably. The Iowa State guide says pile; Foundation Performance Association writers say pier for houses. An anchor is the same steel loaded in tension, such as a tie-back.
Do helical piers lift a house?
They can. A manufacturer says its bracket system can stabilize a structure against further settlement or lift it back toward its original position. Engineers treat stabilizing and lifting as separate goals, and a plan should say which one is intended. Lifting adds stress, so it is designed, not improvised.
Are helical piers better than push piers?
Neither is better in general. Helical piers can be extended deeper and need little vibration or spoil removal, but rocky sites are a disadvantage. Push piers press against the building’s weight and rely on end bearing. The choice depends on soil, loads and access. Our comparison page sets them side by side.
Can helical piers corrode?
Yes. Iowa State says corrosion protection is typical, and that disturbed soil and organic material can speed corrosion. Galvanizing, coatings, extra steel thickness and grout are used. Ask what protection is specified and why.
What does torque have to do with helical piers?
Torque is the turning effort needed to install the pile. In denser soil it takes more torque, and installers relate that to capacity using a factor from the manufacturer’s testing. The method does not apply on bedrock or when the top plate is too shallow. A designer applies a safety factor.
How long do helical piers last?
Lifespan depends on the steel, protection and soil chemistry, so we give no number. Foundation Performance Association writers note that corrosion can limit life expectancy even when steel is galvanized. Ask for the corrosion design basis and the warranty in writing.
How much do helical piers cost?
We do not publish prices. The main drivers are the pier count, shaft size, depth, corrosion protection, access, engineering and permits. Because final length is often only estimated at bid, ask how extra depth is charged. Our cost guide and calculator show how quotes are built.
Sources
- Iowa State University Bridge Engineering Center and InTrans, Helical Pile Foundation Guide for Bridge Structures (October 2023), retrieved .
- Hubbell Power Systems (CHANCE), Technical Design Manual, Edition 3 (2014): helical pile and bracket sections. Manufacturer document, retrieved .
- Foundation Performance Association, FPA-SC-01-0: Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils (2004), section 5.1.5 Helical Piers, retrieved .
- Foundation Performance Association, FPA-SC-08-1: Design, Manufacture, and Installation Guidelines of Precast Concrete Segmented Piles for Foundation Underpinning (2014), retrieved .
- Hubbell Power Systems, Foundation Solutions blog: Push Piers, Frictional or End Bearing? Manufacturer document, retrieved .
- Federal Highway Administration, Drilled Shafts: Construction Procedures and LRFD Design Methods, GEC 10, FHWA-NHI-10-016 (May 2010), retrieved .
- North Carolina Board of Examiners for Engineers and Surveyors, Foundation Repair Guidelines (revised 10/22/2024), 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, parts, installation procedure, torque correlation limits and corrosion notes come from Iowa State University’s helical pile guide for bridges (scope: bridges, used here only for general mechanics).
Residential repair and expansive soil notes come from a Foundation Performance Association committee paper and one manufacturer technical manual, labeled as manufacturer documents. Licensing statements come from the North Carolina engineering board.
No numeric capacity, torque, depth or spacing values are given. No prices. Rules checked 2026-10-14. General information, not engineering advice.
Suggest a correction. We fix errors and say what changed.