Helical Piers
This page explains what helical piers are, how they work, when they're actually appropriate for foundation support, and when other approaches make more sense—helping building owners evaluate recommendations without sales pressure.
Helical Piers: What They Are — and When They Make Sense
Helical piers are frequently mentioned during foundation evaluations and repair estimates.
For many building owners, the term appears suddenly — often without context about what the system is, why it's being suggested, or what alternatives might exist.
Understanding helical piers begins with understanding what they do, how they work, and — most importantly — when their use is actually appropriate.
Hearing the term during an evaluation does not automatically mean they are necessary, nor does it mean your foundation is failing.
This page explains helical pier systems without sales language. The goal is to help building owners recognize when helical piers may be a reasonable solution and when other approaches might be more appropriate.
Topics
What Helical Piers Are
How They Transfer Load
When They're Appropriate
When They're Not
Installation Considerations
Common Misconceptions
Comparison with Other Foundation Support Methods
Questions Building Owners Should Ask
Digging Deeper
Why Torque Alone Doesn't Guarantee Capacity (under construction)
Distinguishing Moisture Problems from Bearing Capacity Deficiency (under construction)
When Monitoring Makes More Sense Than Immediate Underpinning (under construction)
Related Topics
Push Piers: How They Work and When They're Used (under construction)
Underpinning: What It Is and What It Isn't
Differential Settlement: Why Uneven Movement Matters
Material Behavior in Homes: Why Cracks Form and When They Matter
What helical piers are:
A helical pier is a steel shaft with one or more helical bearing plates (resembling large screws) 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.
Components of a helical pier system
Helical pier systems typically include:
Lead section with helical bearing plates (usually 8 to 14 inch diameter)
Extension shafts to reach target depth
Foundation bracket to connect pier to structure
Coupling system to join shaft sections
The specific configuration varies based on site conditions, load requirements, and engineering specifications.
How helical piers differ from other underpinning methods
Helical piers are installed through rotation rather than driving or excavation.
This distinction affects installation speed, equipment requirements, and suitability for different soil conditions.
Unlike driven piles (which rely on displacement and friction) or drilled piers (which require concrete placement), helical piers develop capacity through the bearing area of the plates combined with shaft friction.
This makes them adaptable to sites where vibration or excavation is limited.
How they transfer load
Helical piers transfer structural load to soil through a combination of bearing and friction.
Understanding this process helps clarify both the strengths and limitations of the system.
Bearing capacity of helical plates
The helical plates create bearing surfaces at depth. As load is applied, the plates compress the soil beneath them.
The combined area of all plates determines the total bearing capacity available.
Capacity increases with:
Larger plate diameter
Greater number of plates
Placement in higher-capacity soil
Plate spacing also matters. Plates placed too close together may not develop independent bearing capacity if their stress zones overlap.
Shaft friction
In addition to bearing, the shaft develops friction along its length as it contacts soil.
This friction contributes to total capacity but is generally less reliable than bearing capacity in most residential foundation applications.
Shaft friction is more significant in cohesive soils (clays) than in loose granular soils (sands). In weak or recently disturbed soils, shaft friction may be negligible.
Installation torque as a capacity indicator
During installation, torque (rotational resistance) is measured and recorded.
Many manufacturers correlate torque to capacity using empirical relationships.
This correlation works reasonably well in uniform soils, but it has limitations:
Torque can spike in hard layers that provide minimal bearing capacity (e.g., cemented caliche or gravel lenses)
Torque may remain low in compressible soils that will settle under sustained load
Different soil types produce different torque-to-capacity ratios
Relying solely on installation torque without understanding subsurface conditions introduces uncertainty.
This is why geotechnical investigation before installation is preferred in engineered applications.
When they're appropriate
Helical piers are a reasonable solution in specific conditions.
Their appropriateness depends on soil profile, structural load, access limitations, and whether the underlying problem has been correctly identified.
Conditions where helical piers tend to perform well
Helical piers are often appropriate when:
Competent bearing soil exists at accessible depth (typically 10–30 feet)
Surface soils are weak, compressible, or subject to moisture-related volume change
Installation must occur with minimal vibration or excavation
Access is limited (tight spaces, existing structures)
New construction or additions require deep foundation support
Engineering analysis has identified bearing capacity deficiency as the cause of movement
When geotechnical investigation supports their use
The strongest case for helical piers exists when subsurface investigation confirms:
Soil stratification (what layers exist and at what depths)
Bearing capacity at various depths
Presence of suitable bearing strata within reach
Absence of subsurface obstructions
Without this information, installation depth and capacity become educated guesses rather than engineered solutions.
Applications beyond repair
Helical piers are widely used in new construction applications where their performance is well understood:
Support for decks, porches, and light structures
Foundations in areas with known poor surface soils
Temporary structures requiring removable foundations
Boardwalks, signs, and utility structures
In these cases, geotechnical conditions are typically verified before design, and piers are specified based on known soil properties.
When they're not
Helical piers are not appropriate in all situations.
There are conditions where other solutions are more effective, or where foundation support is not the underlying problem at all.
When the problem isn't bearing capacity
Helical piers address load support.
They do not resolve:
Drainage problems that cause soil saturation
Ongoing moisture infiltration beneath slabs
Seasonal soil expansion and contraction
Plumbing leaks introducing water below grade
Inadequate surface water control
Installing deep foundation support when the actual cause is moisture-related movement does not address the mechanism driving the problem.
In some cases, piers may stabilize elevation while the underlying issue continues.
When movement has already stopped
Not all foundation movement requires intervention.
Settlement that occurred during initial construction, soil compression from one-time loading, or historic movement that has stabilized may not justify underpinning.
If monitoring shows no ongoing change, the structure may have reached equilibrium. Installing piers in this case adds cost without addressing active distress.
When soil conditions are unfavorable
Helical piers may not be suitable when:
Competent bearing soil is too deep to reach economically
Subsurface obstructions (rock, debris, old foundations) prevent installation
Soil layers provide high installation resistance but low bearing capacity
Ground conditions vary significantly across the site
In these cases, alternative foundation support methods — or different approaches entirely — may be more appropriate.
When cosmetic cracking is misinterpreted
Concrete shrinkage cracks, drywall settlement cracks, and material-related movement are often visible without any foundation distress.
Helical piers do not address material behavior.
The presence of cracks does not automatically indicate foundation failure or the need for underpinning. Evaluation should distinguish between material behavior and structural movement.
Installation considerations
Understanding how helical piers are installed helps building owners recognize what to expect during the process and what questions to ask before work begins.
Equipment and access requirements
Helical piers are installed using hydraulic torque motors mounted on various equipment types:
Compact skid steers or mini excavators for tight access
Larger track equipment for open areas
Hand-held equipment for extremely limited access
The choice of equipment affects installation speed, depth capacity, and torque monitoring capability. Smaller equipment may limit maximum torque and therefore achievable capacity.
Depth determination
Installation continues until one of several conditions is met:
Target torque is achieved (indicating estimated capacity)
Practical refusal (equipment cannot advance further)
Predetermined depth based on geotechnical data
Without subsurface investigation, depth is determined by installation resistance alone. This may or may not correspond to optimal bearing soil.
Load transfer to foundation
Once installed, piers must be connected to the foundation and loaded.
This typically involves:
Excavating to expose the foundation
Attaching a bracket to the foundation and pier
Applying hydraulic pressure to transfer load
The amount of lift (if any) is determined during this process. Lift is not always necessary or desirable — stabilization may be the appropriate goal.
What installation does not include
Standard helical pier installation typically does not include:
Correction of drainage issues
Repair of interior finishes damaged by movement
Addressing plumbing or moisture problems
Cosmetic crack repair
Building owners should clarify the full scope before work begins to avoid misunderstanding what the installation will and will not address.
Common misconceptions
Several assumptions about helical piers appear frequently in sales conversations.
Addressing these directly helps building owners make better-informed decisions.
"Helical piers are the only solution"
Helical piers are one foundation support option among several.
Other methods — including push piers, drilled piers, grade beams, and in some cases non-structural solutions like improved drainage — may be equally or more appropriate depending on conditions.
The right approach depends on soil profile, structural configuration, access, and the actual cause of distress.
"Installation torque guarantees capacity"
Torque correlates with capacity under specific conditions, but it is not a direct measurement.
High torque can occur in soils with minimal long-term bearing capacity (e.g., dense gravel or cemented layers), while adequate bearing soils may produce lower torque readings.
Torque is a useful installation parameter, but it does not replace geotechnical evaluation or load testing when capacity verification is critical.
"Deeper is always better"
Effective foundation support depends on reaching competent soil, not simply achieving maximum depth.
Installing piers deeper than necessary adds cost without additional benefit.
Conversely, stopping installation before reaching adequate bearing soil — even at significant depth — does not provide the intended support.
"Piers fix all foundation problems"
Piers address load support.
They do not resolve moisture infiltration, drainage deficiencies, plumbing leaks, or soil expansion. If these conditions caused the original movement, they may continue after pier installation unless separately addressed.
"Every crack requires underpinning"
Most cracking in residential construction results from normal material behavior — concrete shrinkage, drywall settlement, thermal movement.
These occur without foundation distress.
Evaluation should distinguish between cosmetic cracking and movement indicating structural concern. Not all visible cracking justifies helical pier installation.
Comparison with other foundation support methods
Helical piers are one approach to foundation support.
Understanding how they compare to alternatives helps clarify when each method is most appropriate.
Helical piers vs. push piers
Push piers (also called resistance piers or driven piers) are hydraulically driven into the ground using the structure's weight as resistance.
Unlike helical piers, they develop capacity primarily through friction and end bearing after being driven to refusal.
Key differences:
Helical piers are installed by rotation; push piers by hydraulic force
Helical piers provide capacity correlation through torque; push piers through driving resistance
Helical piers work well in softer soils; push piers may perform better in dense or obstructed conditions
Neither is universally superior. Soil conditions and structural requirements determine which is more appropriate.
Helical piers vs. drilled concrete piers
Drilled piers involve excavating a shaft to depth, placing reinforcement, and filling with concrete. This creates a monolithic support element with high capacity.
Drilled piers may be preferred when:
Very high loads must be supported
Soil conditions are suitable for drilling
Access allows for drilling equipment
Helical piers may be preferred when access is limited, installation must be rapid, or conditions favor rotational installation over drilling.
When non-structural solutions are more appropriate
In some cases, foundation support is not the answer.
Improved drainage, moisture management, plumbing repair, or simply monitoring over time may be more appropriate than any underpinning system.
The decision to install helical piers — or any foundation support — should follow evaluation of the underlying cause, not simply the presence of visible symptoms.
Questions building owners should ask
Before committing to helical pier installation, building owners should understand what information supports the recommendation and what alternatives exist.
About the problem
What caused the movement being observed?
Is movement ongoing, or has it stabilized?
What evidence indicates bearing capacity deficiency rather than moisture or drainage issues?
Has geotechnical investigation been performed?
About the proposed solution
Why are helical piers recommended over other foundation support methods?
What depth are piers expected to reach, and why?
How was pier capacity determined?
What happens if adequate bearing soil is not reached?
Will load testing be performed to verify capacity?
About installation
What access is required, and what site impact should be expected?
How long will installation take?
What installation records will be provided?
Will lift be attempted, or is stabilization the goal?
About scope and expectations
What does the proposed work include and exclude?
Are drainage improvements recommended separately?
What warranty or performance guarantee is offered?
What outcome should realistically be expected after installation?
About alternatives
Have other foundation support methods been considered?
Would monitoring before intervention provide useful information?
Are non-structural solutions (drainage, moisture management) appropriate?
These questions help building owners move from passive acceptance to informed evaluation.
Understanding the reasoning behind a recommendation matters as much as the recommendation itself.
A final note
Understanding helical piers — what they are, when they work, and when they don't — allows building owners to participate meaningfully in conversations about foundation repair.
The goal is informed decision-making, not blind acceptance of recommendations.
"Understanding what a solution does is the first step toward knowing whether you need it."