Helical Piers: How They Work and When to Use Them

What Are Helical Piers?

Helical piers (also called helical piles or screw piles) are deep foundation elements made from steel shaft sections with one or more helical plates welded at intervals. Installation involves threading them into the ground with a hydraulic drive head - essentially a very powerful screwdriver.

As the pier is screwed deeper, resistance increases as it reaches more competent soil. Engineers calculate the minimum installation torque that confirms adequate bearing capacity. Additional shaft extensions are added as needed to reach the required depth.

The Three Parts of a Helical Pier

Every helical pier system breaks into three components, and understanding them makes the rest of the process easy to follow.

The lead section carries the helix plates. These are round steel discs pressed to a true helical pitch, usually 3 inches of advance per revolution, so the plate threads through soil instead of augering it out of the way. A residential lead section typically carries one to three plates between 8 and 14 inches in diameter. When multiple plates are used, they are spaced roughly three times the diameter of the plate below so each helix bears on undisturbed soil rather than ground already loosened by the plate ahead of it.

The extension sections are plain shaft with no plates, added in 3-7 foot lengths and coupled with through-bolts or sleeve connections as the pier advances. They carry load down to the helices and provide almost no bearing themselves. That is why a pier can be 40 feet long and still be governed entirely by what happens in the last few feet of soil.

The bracket connects the pier to the house. It seats against the footing and transfers building load into the shaft. Bracket selection depends on footing geometry, and it matters more than most homeowners realize: an undersized bracket or one seated on crumbling concrete becomes the weak link no matter how well the pier below it performs.

The distinction between bearing and shaft is the reason helical piers behave predictably. Nearly all of the capacity comes from end bearing on the helix plates, so the pier either reaches competent soil or it does not, and the installer can tell which happened while the machine is still running.

How Installation Torque Verifies Capacity

This is the single most useful thing to understand about helical piers, and it is what separates them from most other repair methods.

Soil that resists rotation also resists downward load. The harder it is to screw a helix through a stratum, the more bearing that stratum will provide. That relationship has been studied and published for decades, and it is expressed as a torque factor, usually written Kt, specific to each shaft size. Multiply the final installation torque by Kt and you get an estimate of ultimate bearing capacity for that individual pier.

Torque factors vary by manufacturer and are published in each system’s evaluation report, so treat the values above as illustrative rather than as design numbers. The working load is then set by dividing ultimate capacity by a factor of safety, commonly 2.0 for residential underpinning. A pier that finishes at 3,000 ft-lb on a 2.875” shaft would carry roughly 27,000 lb ultimate and be rated around 13,500 lb in service.

What this means for you as a homeowner: every pier under your house has its own measured capacity number, recorded at the moment it was installed. You are not relying on a soil report from three lots away or on the crew’s judgment about when the ground felt firm. If pier 7 finishes 900 ft-lb short of specification, that shows up in the log and the pier gets driven deeper or a helix configuration gets changed. Few other foundation underpinning methods give per-element verification this direct.

Torque is also read continuously rather than only at the end. A pier that climbs steadily, plateaus, then climbs again is telling the operator it passed through a soft lens into a bearing layer. A pier that spikes suddenly at 6 feet has probably hit a boulder or an old footing, not competent soil, and an experienced operator will recognize the difference in the way the reading behaves rather than simply stopping at the number.

Why No Reaction Load Is Needed

A push pier is driven, not turned. The hydraulic ram pushes the pier down by pushing up against the footing, which means the weight of the building is the only thing holding the ram in place. If the structure above cannot supply enough dead load, the house lifts before the pier advances and the installation stalls.

Helical piers sidestep this entirely. The drive head applies rotation, and the helix plates pull the shaft down under their own geometry. The machine can be mounted on a mini excavator, a skid steer, or a portable frame anchored to the ground. Nothing about the process depends on how heavy the building is.

That difference decides the method on a large share of real projects:

• Detached garages and outbuildings rarely carry enough load at the footing for driven piers, especially slab-on-grade garages with thin edge beams.
• Porches, stoops, and covered entries are light, often poorly tied to the main structure, and among the most common settlement complaints.
• Decks and sunrooms frequently have no continuous footing at all, and helical piers can be used as the foundation elements themselves rather than as a retrofit.
• Room additions are the classic case: the original house is on one soil profile, the addition sits on backfill placed decades later, and the addition alone cannot supply reaction load.
• New construction has no structure to push against yet, which rules out driven piers by definition.
• Interior slab locations carry a fraction of the load the perimeter footing does, so reaction force is usually inadequate even inside a heavy house.

The same geometry gives helical piers a second capability push piers do not have. Because the plates bear in both directions, a helical pier resists uplift as well as compression. That is why the same hardware shows up as tiebacks for bowing basement walls, as anchors for retaining walls, and as hold-downs for light structures in high wind areas.

How Helical Piers Are Installed

1. Site layout - Pier locations are marked per the engineer’s or contractor’s plan. For perimeter work, access trenches are dug; for interior work, slab core holes are drilled.
2. Lead section installation - The lead section (with helical plates) is connected to the drive head and advanced into the ground.
3. Extension sections - Plain pipe extensions are added as the lead advances, extending the pier to required depth.
4. Torque monitoring - Installation torque is monitored throughout and logged. Installation stops when minimum torque is achieved.
5. Bracket installation - A foundation bracket is welded or bolted to the pier shaft and attached to the foundation footing.
6. Lifting - Hydraulic jacks at each pier position simultaneously apply load to lift the structure toward target grade.
7. Lock-off - Load is locked into the bracket. Slab patches and access pits are completed.

What Each Step Actually Involves

Excavation is smaller than people expect. A perimeter access pit is roughly 2 feet square and deep enough to expose the bottom of the footing, commonly 2-4 feet. Sod is usually cut and set aside in sheets so it can be relaid. Shrubs within about 3 feet of the wall generally have to come out, and some do not survive the move. Concrete flatwork such as a patio or walkway at the pier location has to be saw cut and patched, and the patch will not match the surrounding color.

Load transfer is the moment that matters. Up to this point the pier is just a rod in the ground. Bringing the bracket into firm contact with sound concrete, then taking the building weight off the failed soil and onto the pier, is what actually stops the settlement. If the footing is spalled, undersized, or cracked at that location, the contractor should say so and repair or reinforce it before loading, not shim over it.

Lift is optional and is a judgment call. Once piers are set, the crew can either stabilize in place or attempt to raise the structure back toward its original elevation. Recovering every fraction of an inch is rarely the right goal. Aggressive lifting can shear cast iron drain lines, open drywall seams, crack tile, and bind door frames that had settled into a working position years ago. Most experienced contractors aim for a practical lift that closes the worst of the differential movement and accept the rest. Ask before work starts which approach is planned and roughly how much lift is expected, then compare that to the laser level readings taken afterward.

Doors and windows often move during lift. This is a good sign structurally, but it means interior touch up is normal: hairline drywall cracks reopening or closing, trim gaps, and doors that need rehanging. Confirm in writing whether cosmetic repair is included, because on most contracts it is not.

Timeline, Noise, and What Gets Disturbed

A typical residential helical pier project runs 2-4 days on site. A small job of 4-6 piers on an accessible perimeter can finish in a single day. Interior piers add time for coring, dust containment, and curing of the slab patch, and full perimeter underpinning on a large home can stretch to a week.

The house stays livable throughout in almost every case. Utilities are not shut off, and the crew works from outside except when interior piers are specified. The main disruptions are practical: driveway access for equipment, spoil piles from the access pits, and a machine running at each location for a few hours at a time.

Noise is moderate and mostly comes from the carrier machine rather than the pier itself. Screwing a pier produces very little ground vibration compared to driven or impact methods, which is a large part of why helical piers get specified near masonry chimneys, plaster walls, historic structures, and buried utilities that would not tolerate hammering.

Two things routinely surprise homeowners. First, the yard will not look the same for a season even with careful backfill, because the pit soil settles and needs topping up. Second, backfill compaction is where corners get cut. Loose backfill against the wall creates a preferential path for surface water straight down to the footing, which can restart the drainage problem that caused the foundation sinking in the first place. Confirm compaction in lifts and positive grade away from the wall is part of the scope.

Access Requirements and Tight-Space Installations

Standard perimeter work uses a torque head mounted on a mini excavator or a compact track loader. Those machines need roughly 4-6 feet of gate or side yard clearance and a route that avoids septic fields, irrigation heads, and shallow utilities. Contractors should call in utility locates before excavating, and on properties with private lines such as gas runs to a pool heater, a private locate is worth the extra cost.

When the machine cannot reach the work, helical piers still can. This is one of the method’s genuine advantages.

• Handheld and portable drive heads run off a remote hydraulic power unit connected by hose. The power unit stays on the driveway and only the drive head and torque indicator have to fit in the workspace.
• Crawlspace installs are feasible in clearances of roughly 30-36 inches using short shaft sections and low-profile heads, which is why helicals dominate crawlspace foundation repair where driven systems cannot be staged.
• Basement and interior slab work uses a core barrel to cut a hole through the slab, then the drive head works vertically from inside. Plastic sheeting and negative air containment should be part of the plan, because concrete coring produces a lot of fine dust.
• Zero lot line and urban sites benefit from the compact footprint. Piers can often be installed from inside the basement when there is no side yard at all.

Tight-access work is slower and priced accordingly, often 10-20 percent above standard perimeter installation. It is still usually cheaper than the alternative, which is removing a deck, a patio, or part of a driveway to make room for full size equipment.

When Helical Piers Are the Right Choice

Helical piers are preferred over push piers in several specific situations:

Interior slab piers: Push piers require substantial dead load as reaction - interior slab areas carry less load than the perimeter footing. Helical piers can be installed from below through core holes without needing the structure’s weight as reaction.

Lighter structures: Detached garages, additions, sunrooms, and lighter residential structures don’t provide enough dead load for push pier installation. Helical piers screw in independently of the structure load.

Limited access: Helical pier drive heads are compact. They can work in tight crawlspace clearances, basements, and locations where larger equipment cannot access.

Tension applications: Helical piers resist both compression (pushing down) and tension (pulling up) loads due to the helical plate geometry. This makes them suitable for wall tiebacks and retaining wall stabilization, where push piers are not appropriate.

Sensitive structures: Helical installation produces less vibration than driven piers, making them preferable near historical structures, sensitive equipment, or existing utilities.

Soil Suitability: Where Helicals Excel and Where They Struggle

Helical piers work across a wider range of soils than most underpinning methods, but they are not universal. The plates have to be able to thread through the profile to reach bearing, which makes obstructions, not soil strength, the real limiting factor.

Expansive clay deserves specific attention because it is where most helical work happens. In Texas, Oklahoma, Colorado, and much of the Front Range and Gulf regions, the top 10-20 feet of soil swells and shrinks seasonally with moisture. A pier that terminates inside that active zone will move with it. Proper design carries the helices well below the seasonal moisture change to soil that stays dimensionally stable year round, and in heaving-prone ground the shaft may also be sleeved so the swelling layer cannot grip and lift it. If your area has a foundation heave history rather than pure settlement, that detail is not optional.

The failure mode to watch for is premature refusal. A pier that hits a boulder, a buried slab, an old cistern, or a construction debris pocket will show high torque without having reached competent bearing soil. The reading looks like success on paper. A careful operator notes the depth, the suddenness of the spike, and whether the torque holds through continued rotation, and will pull and relocate the pier if the evidence points to an obstruction. This is another reason depth records matter alongside torque values: a pier that terminated at 7 feet when neighbors terminated at 24 feet deserves an explanation.

Soil type also drives cost more than any other physical variable, since depth determines how many extension sections each pier consumes. The relationship between ground conditions and pricing is broken down in more detail in the guide to foundation repair cost by soil type.

Helical Piers for New Construction and Additions

Helical piers are not only a repair product. A significant share of installations go into ground that has never carried a structure.

New construction on problem soil. Where a soils report identifies expansive clay, deep fill, high groundwater, or a compressible layer, helical piers can replace conventional spread footings. The building is designed to bear on a grid of piers with grade beams spanning between them, so the structure never rests on the problem stratum at all. This is standard practice in parts of Colorado, Texas, and coastal areas, and it is usually cheaper than over-excavating and replacing soil.

Additions and second stories. Adding a room or a floor increases load on foundations designed for less. Helical piers installed under the new footprint match the settlement behavior of the existing house, which is what prevents the joint between old and new from cracking a year later. Because no reaction load is needed, they can be installed before the addition is framed.

Decks, porches, and accessory structures. Used as primary foundation elements, helical piers replace poured concrete piers entirely. They install in a day, require no concrete cure time, generate no spoil pile, and reach below frost depth reliably. In cold climates this is the main argument: a helix set below the frost line will not be lifted by frost jacking the way a shallow poured pier is.

Modular, manufactured, and light steel buildings. These are exactly the structures too light for driven systems, and they are common helical applications.

New construction piers are typically designed by an engineer working from the soils report, with capacity confirmed by torque during installation. Ask for that design and the installation record even on a new build, because it becomes part of the disclosure package if you ever sell.

Helical Pier Specifications

A helical pier system includes:

• Material: High-strength steel (typically ASTM A36 or A513)
• Corrosion protection: Hot-dip galvanizing (recommended) or fusion-bonded epoxy coating
• Shaft diameter: 1.5” - 3” square bar or 2.875” - 4.5” round pipe, depending on design load
• Helix configuration: Single helix for most residential; multi-helix for higher loads
• Bracket: Load transfer bracket matched to the footing configuration

Ask the contractor for the pier manufacturer’s ICC-ESR evaluation report - this is the industry-standard third-party validation of load capacity for the specific pier system being used.

Corrosion protection is the specification most worth questioning. Hot-dip galvanizing to ASTM A123 adds decades of service life for a small cost increase, and in aggressive soils, meaning low resistivity, low pH, or high chloride content near coastlines and de-iced roadways, it should be considered mandatory rather than an upgrade. Bare black steel piers are sold and installed, and they are the wrong choice to save a few hundred dollars on a repair meant to outlast your ownership of the house.

Helical Piers Compared to Push Piers

The short version: both reach the same stable bearing soil and both transfer load through a bracket at the footing. They differ in how they get down there. Push piers are driven hydraulically using the building as reaction force, which makes them fast and economical on heavy perimeter walls but unusable on light structures, at interior locations, and before a building exists. Helical piers are turned in, which costs a little more per pier and buys installation flexibility plus per-pier torque verification.

In practice most experienced contractors carry both systems and mix them on a single job, using push piers along the main perimeter and helicals under a settling porch or an addition. If you are trying to decide between quotes proposing different systems, the full breakdown is in helical piers vs push piers.

Helical Pier Cost

Helical piers typically cost 10-20% more per pier than comparable push piers because of the more complex manufacturing (helical plate welding) and slower installation (screwing vs. driving). However, for projects where helical piers are the appropriate system, this premium is unavoidable.

Because depth, pier count, access, and local labor rates all move the number substantially, treat the figures above as a starting point rather than a quote. A full breakdown of pricing scenarios, what drives each variable, and how to read an itemized bid is covered in the helical piers cost guide.

Documentation You Should Receive

Helical piers generate real installation data, and that data is the proof the job was done to specification. A contractor who cannot produce it is asking you to take the work on faith. Request these deliverables in writing before signing, not after the crew has left.

Read the torque log against the design requirement rather than just filing it. Every pier should meet or exceed the specified minimum. If several fall short, or several terminated far shallower than the rest, ask for the engineer’s written acceptance of those piers before making final payment.

The elevation survey is the other document people skip. Without a before reading, there is no objective record of how much the floor was out of level, and no way to demonstrate later that the repair held. Keep both readings with your closing documents.

Warranty and Transferability

Helical pier warranties usually run 25 years to lifetime, and the meaningful differences are in the fine print rather than the headline term.

What is covered. Most warranties cover further settlement at the piered locations only. They do not cover settlement elsewhere on the foundation, cracks that appear in unpiered sections, cosmetic finishes, or damage from new plumbing leaks and drainage failures. This is reasonable, but it means the scope of the pier layout effectively defines the scope of the coverage.

Who backs it. A contractor warranty is worth exactly as much as the contractor’s continued existence. Manufacturer-backed warranties administered through a dealer network survive a single company going under. Ask which type you are getting and get the answer in the contract.

Transferability. This is the clause that affects resale value. Some warranties transfer automatically to the next owner, some transfer once for a fee of a few hundred dollars, and some are void on sale. A transferable warranty plus a complete torque log turns a foundation repair from a negotiating liability into documented evidence the problem was fixed properly. The mechanics of coverage and transfer are covered further in the foundation repair warranty guide.

What voids it. Common exclusions include failing to maintain drainage and grading, adding load such as a second story, and allowing plumbing leaks to go unrepaired. Keep gutters discharging away from the wall and grade sloping away, since those are the two conditions a warranty adjuster will look at first.

Contractor Red Flags

Helical piers are an engineered product installed by whoever bought a torque head, and the range of quality in the field is wide. Watch for these:

• No torque monitoring on the machine. If there is no calibrated torque indicator or pressure gauge referenced to a torque chart, capacity is being guessed. Walk away.
• A pier count and price given without measuring anything. A legitimate scope starts with a laser level elevation survey of the floor and a look at crack patterns, not a walk around the outside.
• Refusal to name the pier manufacturer. Generic or shop-fabricated piers without an evaluation report have no published capacity tables, which means the torque readings cannot be converted to verified capacity.
• No engineer involved on anything structural. For significant settlement, a stamped repair plan from a licensed structural engineer working independently of the contractor is the standard. See structural engineer inspection for what that process involves.
• Large deposits demanded up front. Materials deposits are normal. Requests for half or more of the contract before work starts are not.
• Same-day discount pressure. Prices that expire when the salesperson leaves the driveway exist to prevent you from getting a second bid.
• A promise of full lift back to original elevation. No honest contractor guarantees that outcome, because the plumbing and finishes will not always survive it.
• No mention of drainage. Piers stop settlement, they do not fix the water management that often caused it. A contractor who never asks about gutters, downspouts, or grading is selling hardware rather than solving the problem.

More warning signs and the questions to ask each bidder are collected in the foundation repair red flags guide. Get at least two bids, and compare pier count, specified depth, capacity per pier, and warranty terms rather than the bottom line alone.

Related Guides

• Helical piers cost
• Helical piers vs push piers
• Push piers
• Foundation underpinning
• Foundation sinking
• Foundation repair warranty