How Do Helical Piles Work? Installation, Capacity & Benefits Explained

If you have ever wondered how a handful of steel shafts can hold up a house, a deck or an entire solar array, the answer is surprisingly simple: they work like giant screws. Helical piles (also called helical piers, screw piles or helical anchors) are steel deep-foundation elements that are rotated into the ground until their helical plates, called helices, sit in strong, stable soil. From that point on, the pile carries the weight of the structure down past weak surface soils, immediately, with no concrete to pour or cure.

This guide explains how helical piles work, what they are made of, how they are installed, how much they can hold, where they make sense and where they do not. It is written by the team at Northeast Pile Supply, an American-made helical pile supplier serving contractors, builders and homeowners across New England and Florida.

In this guide: what a helical pile is, how the load transfer works, the parts of a pile, round vs. square shafts, step-by-step installation, capacity, helical piles vs. concrete and driven piles, benefits and limitations, applications, New England and Florida considerations, cost factors, how to choose a supplier, and answers to the most common questions.

What Is a Helical Pile?

A helical pile is a deep foundation made from a steel shaft with one or more round steel plates welded to it. The plates are formed into a shallow spiral so the pile can be rotated into the soil the way a screw is turned into wood. In everyday conversation you will hear the same product called a helical pier, screw pile, helical anchor or helical foundation pile. The names overlap, but the idea is identical: a steel foundation element that is screwed, not poured or hammered, into the ground to carry a structure.

Helical piles are used for everything from a backyard deck to commercial buildings, transmission towers and solar farms. Depending on the shaft, the number of helices and the soil, they can be engineered for compression loads that range from well under 1 kN (a few hundred pounds) to more than 5,000 kN (over a million pounds). That range is one reason they have become a go-to solution for both light residential work and heavy engineered structures.

A Short History of Screw Piles

The concept is not new. The screw pile was invented in the 1830s by Alexander Mitchell in the United Kingdom and was first used to anchor marine structures such as lighthouses and moorings. Screw piles were also used along the North American east coast in the late 1800s and early 1900s, and some lighthouses built on them are still standing. Their popularity faded when steam-powered pile drivers made driven piles cheaper to install, then returned decades later when high-torque hydraulic drive motors made installation fast and controllable. Today helical piles are recognized in building codes and covered by industry guidance such as the Deep Foundations Institute's helical pile design guide.

How Do Helical Piles Work?

Every helical pile does its job through three simple ideas: it bypasses weak soil, it bears on strong soil, and it proves its own capacity as it goes in.

1. Helical piles bypass weak soil

A conventional shallow footing is only as good as the top few feet of soil underneath it. In New England and many other regions, those top layers can include organic topsoil, loose fill, soft clay or frost-susceptible silt, none of which make a reliable base. The steel shaft of a helical pile passes straight through those layers, so the weak material no longer decides how the structure behaves.

2. The helices bear on competent soil

The helical plates at the bottom of the shaft act like small, deep bearing foundations. In compression, the soil beneath the plates resists the downward load. In tension (uplift), the soil above the plates resists being pulled out. That is why the same pile type can support a building, tie down a structure against wind or hurricane uplift, or anchor a retaining wall or seawall. Because the plates sit below the zone affected by seasonal moisture change and frost, helical piles are also resistant to the seasonal movement that damages shallow foundations.

3. Installation torque verifies capacity

As the pile is rotated into the ground, the drive head measures the torque it takes to turn it. Dense, strong soil takes more torque than loose or soft soil, and there is an established empirical relationship between final installation torque and the capacity the pile can deliver. Installers watch a digital torque indicator and stop only when the pile reaches the engineered torque and depth. That gives you something poured concrete cannot: a measured, recorded check on every single pile at the moment it is installed.

Many design approaches use a torque correlation factor (often called Kt) to convert final torque into estimated capacity, and values can vary with shaft size and soil conditions. Torque is a powerful quality-control tool, but it does not replace a geotechnical investigation on larger or higher-risk projects. For a light structure such as a deck, an engineer may reasonably design from installation torque alone. For heavier structures, soil borings and, in some cases, on-site load tests give a more complete picture.

The Parts of a Helical Pile

A helical pile is a system of simple components that can be configured in many ways. Understanding each part makes it easier to read a pile specification or compare products.

The shaft

The shaft is the steel column that transmits load from the structure to the helices. It can be a round hollow section (pipe) or a solid square bar. Shaft diameter, wall thickness and length are all design variables, and they control how much torque the pile can take during installation, how much axial load it can carry and how well it resists bending.

The helix plates

The helices are the bearing plates welded to the shaft. A pile can have a single helix or several, and the plates can be different diameters and thicknesses. They are formed at a consistent pitch so that the pile advances into the soil in proportion to how far it turns, instead of grinding or augering the soil. Larger and more numerous helices spread load over more soil, which is how engineers tune a pile to the ground conditions at a specific site.

Extensions and couplings

The first section driven into the ground, the lead section, carries the helices. If the strong soil is deeper than the lead section can reach, plain extension sections are bolted or coupled on and the pile keeps turning. Extensions are quick and relatively inexpensive to add, which is why one pile type can serve a shallow site and a deep one.

Brackets, caps and connections

The top of the pile is cut to the finished elevation and fitted with a cap, bracket or connection plate that ties it to the structure, whether that is a deck beam, a timber or steel frame, a concrete grade beam or the footing of an existing home being underpinned. Getting this connection detail right is as important as getting the pile depth right.

Round Shaft vs. Square Shaft Helical Piles

Both shaft types are used successfully; they simply suit different jobs. Round (pipe) shafts have good stiffness in every direction, so they are often chosen when a pile must resist lateral loads or has unsupported length in soft soils. Solid square shafts are efficient for high-capacity compression and tension work, especially in dense or hard layers where a lot of torque is needed.

At Northeast Pile Supply our helical pile lines include 2.875 helical piles, 3.5 helical piles and 4.5 helical piles, so you can match the shaft size to the load, the soil and the equipment on site. Your engineer or installer should make the final selection for each project.

How Are Helical Piles Installed? Step by Step

Installation is one of the biggest reasons people choose helical piles. There is no excavation of footing trenches, no formwork, no spoil to haul away and no waiting on concrete. Here is how a typical installation unfolds.

1. Site evaluation and engineering. The engineer or installer reviews the structure, the loads and the soil information to determine pile size, helix configuration, spacing and target torque and depth.
2. Layout and utility check. Pile locations are marked out and underground utilities are located before any equipment arrives. Call 811 before digging or driving anything into the ground.
3. Equipment set-up. A hydraulic drive head is mounted on an excavator, mini excavator, skid steer or, for light work, a handheld unit, sized for the torque the job requires.
4. Starting the lead section. The lead section is positioned at the layout mark and rotated into the ground, kept plumb. A good target is within roughly 2 degrees of vertical, advancing steadily in proportion to the helix pitch.
5. Adding extensions. Extension sections are coupled on as the pile advances while the crew watches depth and torque.
6. Reaching target torque and depth. When the pile hits the engineered torque at the required depth, installation stops and the final torque and depth are recorded.
7. Cutting and capping. The shaft is cut to elevation and the cap or bracket is attached.
8. Loading the structure. Because there is no concrete to cure, construction can continue immediately.

What equipment installs helical piles?

Light piles can be turned in with portable torque units, skid steers, mini excavators and even utility trucks. Higher-capacity piles are normally installed with larger excavators or purpose-built drill rigs, because they need more torque, more downward force and more swing resistance. Equipment selection depends on the required installation torque, the torsional strength of the shaft, site access and clearance, and the soil profile.

The drive head is the heart of the system. Our Digga anchor drives range from lightweight units to 1-speed drives rated for thousands of foot-pounds of torque, so contractors can match the attachment to the machine they already own. Torque indicators should be calibrated regularly so the readings recorded for each pile can be trusted.

How long does installation take?

Speed depends on soil, pile length and site access, but a skilled crew with the right machine can install a pile in minutes rather than hours, and a small deck or shed footprint can often be completed in a single day. Because the work is quiet, low-vibration and produces almost no spoil, it is also easier on neighbors, landscaping and tight job sites.

How Much Weight Can a Helical Pile Hold?

There is no single number, because helical piles are engineered for the site. A small-diameter pile under a deck may be designed for a few thousand pounds, while large, multi-helix piles in dense soil can carry many tons each. What a particular pile can hold depends on several things working together.

• Soil strength at the helix depth. This is the biggest factor, and the reason geotechnical information matters.
• Number, diameter and spacing of the helices. More bearing area means more capacity, within the limits of the shaft.
• Shaft size and wall thickness. The shaft must be strong enough to survive the installation torque and carry the working load.
• Installation quality. Plumbness, steady advance and reaching the specified torque all affect real-world performance.
• Load direction. Compression, tension and lateral loads each need to be checked.

Engineers apply a factor of safety on top of the ultimate capacity, and on high-liability projects a load test on a test pile can confirm performance and sometimes allow a leaner, more economical design. If you are unsure what your project needs, talk to an engineer or use our installer directory to find a professional near you.

Helical Piles vs. Concrete Footings and Driven Piles

Helical piles are not the only way to build a foundation, so it helps to see how they compare with the most common alternatives.

Helical piles vs. poured concrete footings

Poured footings need excavation, forms, rebar, concrete delivery and curing time, and they rely on the soil near the surface. Helical piles skip the digging and the waiting, carry load immediately, can be installed through winter weather and reach stronger soil below the frost line. Concrete footings can still be the right choice on firm, well-drained soil with simple loads, but when the soil is poor, the site is tight or the schedule is short, screw piles often come out ahead.

Helical piles vs. driven piles

Driven piles are hammered into the ground with heavy, loud, vibration-producing equipment. Helical piles are screwed in with comparatively small machines, produce little noise or vibration, and give a torque reading on every pile. They can also be removed and reused, which matters for temporary structures. Driven piles can still win on very large, deep projects where massive equipment is already on site.

Benefits of Helical Piles

• Fast installation. No excavation, formwork or curing means shorter schedules and lower labor cost.
• Immediate load capacity. Build on the piles the same day.
• Works in poor soil. Soft, loose, wet or expansive soils are bypassed rather than fought.
• Quiet and low-vibration. A good fit near occupied buildings, neighbors and sensitive sites.
• Minimal site disturbance. Little spoil and no open trenches to restore.
• Verified in the field. Installation torque is measured and recorded pile by pile.
• Strong in tension and compression. Useful for uplift, tie-downs and anchors as well as bearing.
• Frost-resistant. Helices set below the frost line resist heave, and installation can continue in cold weather.
• Easy access. Compact equipment can reach backyards, crawl spaces and areas around existing structures.
• Adjustable on site. Extensions can be added if the strong layer is deeper than expected.
• Removable and reusable. Piles can be backed out for relocation or site restoration.
• Long service life. Hot-dip galvanizing and added steel thickness extend durability in corrosive soils.

Limitations: When Helical Piles Are Not the Right Fit

No foundation is right for every project, and a good supplier will tell you so. Keep these limitations in mind.

• Very shallow bedrock or refusal. If solid rock or an obstruction sits within a few feet of the surface, the pile cannot be screwed to a useful depth. Piles cannot penetrate bedrock.
• Boulders and cobbles. Glacial till can hide large stones. A pile that hits an obstruction can usually be backed out and relocated, but torque-to-capacity predictions are less certain in boulder-rich soils.
• Very dense layers. Hard layers may call for a heavier shaft or pre-drilling.
• Lateral and bending loads. Small-diameter shafts are less stiff, so high lateral loads may need larger shafts, battered (angled) piles, pile caps or grade beams.
• Installer experience. Results depend heavily on the installer's equipment, training and honesty. Choose a qualified contractor.
• Engineering still matters. Look-alike products, such as ground screws or low-quality anchors, are not the same as engineered helical piles and should not be substituted.

Where Helical Piles Are Used

Helical piles have outgrown their marine roots. Here are the most common applications, with links to our detailed guides for each.

Decks and porches

Helical piles let you build a deck without digging big footing holes, even in frost-prone or poorly drained ground. Learn more in our guide to helical piles for decks.

Sheds and outbuildings

A shed on helical piles stays level season after season and can be set up quickly. See helical piles for shed foundations.

Cottages and cabins

Seasonal homes on sloped, wooded or sensitive lots benefit from low-impact installation. Read about helical piles for cottage foundations.

House foundations and additions

New homes, additions and raised structures can sit on engineered piles instead of full excavations. Details are in helical piles for house foundations.

Foundation repair and underpinning

Settling foundations can be stabilized, and often lifted, by installing piles beneath the existing footing and transferring load to deeper soil. See helical piles for foundation repair.

Docks, piers and marine structures

Helical piles started their life supporting marine structures, and they remain a strong choice for docks, boardwalks and seawall tiebacks. Explore helical piles for dock foundations.

Solar arrays, towers and retaining walls

Ground-mount solar, communication and transmission towers, and retaining walls all use helical piles for fast, adjustable foundations and anchors. See helical piles for solar panels, or browse all helical pile applications.

Helical Piles in New England and Florida

Soil, climate and code requirements change from region to region, and so does the way helical piles are designed and installed. We supply both of the regions we know best.

New England: frost, till and ledge

In New Hampshire, Massachusetts, Maine, Vermont, Connecticut and Rhode Island, frost depth, glacial till, boulders and shallow ledge shape most foundation decisions. Helical piles help because the helices bear below the frost line, installation can continue in cold weather, and a pile that meets an obstruction can be relocated. Review our areas we serve for helical pile supply near you, and note that we offer pickup in New Hampshire, which has no state sales tax.

Florida: sandy soils, high water tables and storms

In Florida, loose sandy soils, a high water table and hurricane-driven uplift and wave forces are the main concerns. Helical piles reach deeper bearing layers, resist uplift in tension, and are widely used for docks, seawall and bulkhead tiebacks and storm-resilient foundations. See our Fort Myers, Florida helical pile supplier page for local information.

What Affects the Cost of a Helical Pile Foundation?

Pricing varies widely, so be wary of any single per-pile number that does not account for your site. The main cost drivers are the number of piles, shaft size and helix configuration, depth to competent soil, access and equipment, galvanizing or corrosion protection, engineering and permitting, and the cost of connecting the piles to the structure.

Helical piles can look more expensive per foundation point than a simple concrete footing, but the full picture often favors them: no excavation, no formwork, no concrete delivery, no curing delay and less restoration work. On poor soils, the savings in time and risk can be substantial. The best way to know your number is to get quotes from qualified installers using the same design.

How to Choose Helical Piles and a Supplier

Quality varies between manufacturers. Look for engineered capacities backed by data, quality mill-grade steel and certified welds, galvanized or otherwise protected shafts, proper torque ratings on the shaft and couplings, and a supplier who can support your installer with the drives and accessories they need.

Why contractors choose Northeast Pile Supply: our helical piles are American made with patented inertia-welded construction, we serve both New England and Florida, we carry the Digga anchor drives to install them, and customers who pick up in New Hampshire pay zero sales tax. We are a family-owned and operated business, so you talk to people who know the product.

Helical Piles FAQ

What is a helical pile?

A helical pile is a steel deep foundation with one or more helical plates welded to the shaft. It is screwed into the ground until the plates reach strong soil, then it supports the structure above. It is also called a helical pier, screw pile or helical anchor.

How do helical piles work?

They pass through weak surface soil and transfer the structure's load to stronger soil at depth through the helical bearing plates. Installation torque is measured as the pile goes in, which verifies the capacity in the field.

How deep do helical piles go?

Depth depends on where competent soil is found. Piles for light structures can be a few feet to a dozen feet or more, and deeper piles are built by adding extension sections. Your engineer sets the depth and target torque for the site.

How long do helical piles last?

Service life depends on the soil's corrosivity and the protection used. Hot-dip galvanizing, additional steel thickness and, in severe cases, sacrificial anodes can extend durability, and many installations are designed for decades of service.

Do helical piles need concrete?

The piles themselves do not. The structure is attached with a cap or bracket, although some designs tie piles into a concrete grade beam or footing at the top. There is no curing time before loading.

Can helical piles be installed in winter?

Yes. Because there is no concrete to cure, they can be installed in cold weather, including through frozen ground with the right equipment, which is a major advantage in New England.

Can helical piles lift a settled foundation?

In many cases they can stabilize and raise a settled foundation. Piles are installed beneath the footing, transfer load to deeper soil and brackets are used to lift the structure to the desired elevation. A structural engineer should evaluate the building first.

Do I need an engineer for helical piles?

For most projects, yes. Engineers size the piles to the loads and soils, and many building departments require stamped plans. For small, low-risk structures an engineer may base the design on installation torque, but you should always confirm local requirements.

Key Takeaways

• Helical piles are steel screw-in foundations that transfer load past weak soil to strong soil.
• Installation torque gives a real-time, recorded check on each pile's capacity.
• They install quickly, quietly and without concrete curing, even in winter.
• They are best suited to poor soils, tight sites, repairs and projects where speed matters.
• They are not suited to very shallow bedrock, and boulders can complicate installation.
• Good engineering, quality steel and an experienced installer determine performance.

Sources and Further Reading

• Coastal Foundation Solutions: What Is a Helical Foundation Pile?
• Structural Engineering Basics: Helical Piles
• Bustamante Engineers: What Are Helical Piles, How Do They Work and Why Use Them?
• Northeast Pile Supply: Helical Piles, The Complete Guide
• Northeast Pile Supply: What Are Helical Piles? Benefits, Installation and When to Use Them

This article is general information, not engineering advice. Pile selection, depth, spacing and capacity must be determined by a qualified engineer for your specific site and local code.