This page is about what helical piers are, how they carry load into competent soil, and when documented conditions actually call for them. Hearing the term on an estimate does not mean you need them.
What helical piers are
A helical pier is a steel shaft with one or more helical bearing plates welded to it. The system is installed by rotating it into the ground until it reaches soil capable of supporting structural load.
Once installed, the pier transfers load from the foundation to deeper, more competent soil layers. The helical plates function as anchors, distributing load across multiple depths rather than relying solely on friction along the shaft.
Basic components
- Lead section with helical bearing plates (typically 8–14 inch diameter)
- Extension shafts to reach target depth
- Foundation bracket connecting pier to structure
- Coupling system joining shaft sections
Unlike driven piles or drilled concrete piers, helical piers develop capacity through the bearing area of the plates combined with shaft friction — installed by rotation rather than driving or excavation.
Helical piers transfer structural load through a combination of bearing and friction.
Bearing capacity of helical plates
The helical plates create bearing surfaces at depth. Capacity increases with larger plate diameter, greater number of plates, and placement in higher-capacity soil. Plate spacing matters — plates too close together may not develop independent bearing if stress zones overlap.
Shaft friction
Shaft friction contributes to total capacity but is generally less reliable than bearing in most residential applications. More significant in cohesive soils (clays) than loose granular soils.
Installation torque
Torque is measured during installation and often correlated to capacity — but this correlation has limits. High torque can occur in hard layers with minimal long-term bearing capacity; adequate bearing soils may produce lower torque readings. Torque does not replace geotechnical investigation.
Helical piers tend to perform well when:
- Competent bearing soil exists at accessible depth (typically 10–30 feet)
- Surface soils are weak, compressible, or moisture-sensitive
- Installation must occur with minimal vibration or excavation
- Access is limited (tight spaces, existing structures)
- Engineering analysis identifies bearing capacity deficiency as the cause
The strongest case exists when subsurface investigation confirms soil stratification, bearing capacity at depth, suitable bearing strata within reach, and absence of obstructions — not when depth is guessed from installation resistance alone.
When the problem isn't bearing capacity: Helical piers address load support. They do not resolve drainage problems, moisture infiltration, plumbing leaks, or seasonal soil expansion. Installing piers when moisture is the cause may stabilize elevation while the underlying issue continues.
When movement has stopped: Historic settlement that has stabilized may not justify underpinning. If monitoring shows no ongoing change, the structure may have reached equilibrium.
When cosmetic cracking is misinterpreted: Most residential cracking results from material behavior — shrinkage, thermal movement — not foundation distress. Evaluation should distinguish between the two before underpinning is recommended.
Installation uses hydraulic torque motors on skid steers, mini excavators, or hand-held equipment depending on access. Depth is reached when target torque is achieved, practical refusal occurs, or predetermined depth from geotechnical data is met.
Standard installation typically does not include drainage correction, interior finish repair, plumbing fixes, or cosmetic crack repair. Clarify scope before work begins.
"Helical piers are the only solution" — Push piers, drilled piers, grade beams, and non-structural drainage solutions may be equally or more appropriate.
"Torque guarantees capacity" — Useful parameter, not a direct measurement. Does not replace geotechnical evaluation or load testing when verification is critical.
"Deeper is always better" — Effective support means reaching competent soil, not maximum depth.
"Every crack requires underpinning" — Evaluation should distinguish cosmetic material behavior from structural movement.
vs. push piers: Installed by hydraulic force against structure weight; capacity through driving resistance. May perform better in dense or obstructed conditions. Neither is universally superior.
vs. drilled concrete piers: Preferred for very high loads and suitable drilling conditions. Helical piers preferred for limited access and rapid installation.
Non-structural alternatives: Improved drainage, moisture management, monitoring, or plumbing repair may be more appropriate than any underpinning system.
Questions building owners should ask
- What caused the movement — and is it ongoing or historic?
- What evidence indicates bearing deficiency rather than moisture or drainage?
- Why helical piers over other methods — and what depth is expected?
- How was capacity determined? Will load testing be performed?
- What does the scope include and exclude?
- Have monitoring or non-structural alternatives been considered?
Digging deeper
Why Torque Alone Doesn't Guarantee Capacity
Published article
Underpinning is not a diagnosis
Published article
Micropiles
Related method
Understanding what a solution does is the first step toward knowing whether you need\u00a0it.