How Deep Do Helical Piles Go? Typical Depths & What Sets Them

Helical piers are usually installed 10 to 30 feet deep, according to manufacturer Ram Jack, but there is no fixed depth. A helical pile is screwed down until its helix plates reach soil strong enough to carry the load, which the installer confirms by measuring installation torque. It must also clear minimum-depth rules tied to the helix size and the local frost line, so the final depth is whatever satisfies all of those at once.

Key takeaways

• Typical range: about 10 to 30 feet for foundation piers, with shallower piles possible for light structures on firm soil and much deeper piles in soft ground.
• Torque sets the stopping point: capacity is estimated from final torque using Qult = Kt × T, a method recognized in IBC Section 1810.3.3.1.9.
• Minimum depth rules apply: CHANCE recommends at least 5 helix diameters below the bottom of the foundation, and tension piles in ICC-ES reports need 12 helix diameters of cover.
• Frost matters: the helix should sit below the maximum frost penetration plus at least one helix diameter.
• Depth is not known until installation: quotes include a standard length, and extra extensions are added in the field if firm soil is deeper.

How deep do helical piers go?

Most residential and light commercial helical piers end up in the 10 to 30 foot range reported by Ram Jack. That range is useful for planning, but your pile depth depends on your site.

A pile in dense sand or stiff clay may reach its target torque quickly. A pile in soft clay, loose fill, or organic soil may need several extension sections before the helix finds competent soil. That is why contractors price piles to a standard depth and then charge for extra length, as our helical pier cost guide explains.

What determines how deep a helical pile goes?

CHANCE, one of the largest helical pile manufacturers, sums up the design with two questions: what are the soils, and what are the loads (Hubbell). Depth falls out of the answers.

How does installation torque relate to capacity?

As a helical pile advances, the drive head has to work harder in stronger soil. That resistance, the installation torque, correlates with the pile's axial capacity. The relationship is Qult = Kt × T, where Qult is ultimate capacity, T is final installation torque, and Kt is an empirical torque correlation factor (Hubbell). The IBC recognizes "well-documented correlations with installation torque" as one of the accepted ways to determine helical pile capacity (IBC 1810.3.3.1.9).

Kt gets smaller as shaft size gets bigger. The CHANCE evaluation report ICC-ES ESR-2794 lists these values:

Here is how that translates into a stopping point. Suppose a pier needs an allowable capacity of 10,000 pounds and the engineer uses a safety factor of 2. The ultimate capacity must be 20,000 pounds. With a 1.75-inch square shaft (Kt = 10), the required final torque is 20,000 ÷ 10 = 2,000 ft-lb. The installer keeps adding extensions until the torque gauge reads at least 2,000 ft-lb, and the depth at that moment becomes the pile's depth. Under the IRC without a soil report, ESR-2794 requires a safety factor of 2.5, which would raise the target to 2,500 ft-lb. For more on capacity, see how much weight a helical pile can hold.

ESR-2794 also defines how the final torque is read: for tension piles and multi-helix compression piles, it is the average of the last three readings taken at 1-foot intervals over the final 2 feet of installation. That prevents one spike from a rock or root from being treated as proof of capacity.

What is the minimum depth for a helical pile?

Reaching torque is not enough on its own. Several rules keep the helix from sitting too close to the surface:

• Five diameters below the foundation. CHANCE recommends a minimum of 5 times the diameter of the largest helix below the bottom of the foundation (Hubbell). For a 10-inch helix, that is just over 4 feet.
• Three diameters below seasonal soil movement. The same guidance calls for 3 helix diameters below the zone affected by seasonal changes such as frost.
• Twelve diameters for tension. ESR-2794 requires the top helix of a tension pile to be at least 12 times the largest helix diameter below the ground surface unless an engineer justifies less. For a 12-inch helix, that is 12 feet. Supportworks notes that AC358 established its torque factors under tension loading at depths of 12 plate diameters or more (Supportworks).

The engineer uses whichever rule gives the deepest result, then adds the torque requirement on top.

How deep do helical piles need to be below the frost line?

Frost is often the controlling factor for decks, porches, and other light structures in northern states. Freezing soil bonds to a pile shaft (called adfreeze) and can jack a lightly loaded pile upward. CHANCE advises embedding the helix below the zone of maximum frost penetration plus at least one helix diameter, and notes that frost can reach up to 6 feet in northern latitudes (Hubbell). In one field comparison it cites, a helical pile heaved about 0.2 inches over a winter while a drilled concrete pier heaved about 1.4 inches.

Your local frost depth is set by your building department in the IRC's climate and geographic design criteria table. Deck footings must extend below it under IRC Section R507.3. Our guide to helical piles for decks covers the deck-specific rules.

Why can't the installer tell you the exact depth up front?

Soil changes across a site, sometimes within a few feet. A soil boring shows conditions at one point, and many residential jobs have no boring at all. The pile itself acts as a probe: its torque readings reveal soil strength foot by foot. A good installer quotes a standard length per pile, states the per-foot cost for extra length, and gives you a torque and depth log for every pile when the job is done.

The same uncertainty affects schedule. Deeper piles need more extensions and more time; see how long it takes to install a helical pile. Spacing can also change if deep soft soil calls for more piles, which our article on helical pier spacing explains.

Is a deeper helical pile always better?

Not necessarily. Deeper piles cost more, and past a certain point extra depth adds little in granular soil. Supportworks notes that effective overburden pressure in granular soil is limited by a critical depth, often taken as a conservative 20 feet in design. The goal is to reach competent soil with the required torque, meet the minimum-depth rules, and stop. Depth also has little to do with corrosion; soil chemistry matters more, as covered in do helical piers rust.

If you are comparing foundation options for a site with deep soft soil, our guide to helical piles vs. concrete shows where each one fits. You can also find experienced local installers in the Helical Pile USA state directory, including deep-frost markets such as Minnesota and North Dakota and soft-soil markets such as Louisiana. Installers and manufacturers can get featured on Helical Pile USA to reach people researching depth and design.

Frequently asked questions

How deep do helical piers go for a house?

Usually 10 to 30 feet, according to Ram Jack. The actual depth is wherever the pile reaches the torque that proves its capacity while meeting minimum-depth and frost rules.

What is the minimum depth for a helical pile?

It depends on helix size and loading. CHANCE recommends at least 5 helix diameters below the foundation, and ICC-ES reports require 12 helix diameters of cover for tension piles unless an engineer justifies less.

How is helical pile depth determined?

By installation torque. The installer adds extensions until the final torque meets the value calculated from the design load, the safety factor, and the torque correlation factor for that shaft.

Do helical piles have to go below the frost line?

In frost-prone areas, yes. The helix should sit below the maximum frost penetration plus at least one helix diameter so it anchors in unfrozen soil.

Can helical piles hit bedrock?

They can, and shallow rock may stop a pile before it reaches the required embedment. The engineer may then approve a shorter pile based on torque and site conditions, relocate the pile, or specify a different system.