Understanding ICC-ES AC358: A Simple Breakdown

Table of Contents

• The Critical Role of ICC-ES AC358 in Helical Pier Compliance
• What ICC-ES AC358 Defines for Helical Foundation Systems
• Corrosion Protection, Soil Requirements, and Load Testing Under AC358
  • Soil Classification and Installation Criteria
  • Corrosion Protection Strategies for Varying Soil Types
  • Load Testing Protocols and Documentation
• Applying AC358 Compliance in Helical Pier Installations
  • Pre-Installation Documentation and Engineering Review
  • Torque Correlation and Capacity Verification During Installation
  • Post-Installation Inspection and Reporting
• Advanced Engineering Considerations for AC358 Compliance
• Common Questions About ICC-ES AC358 Compliance
• Building Long-Term Performance Through ICC-ES AC358 Compliance

The Critical Role of ICC-ES AC358 in Helical Pier Compliance

For helical pier systems to meet building-code requirements, they must satisfy the ICC-ES AC358 helical pile acceptance criteria, a rigorous standard published by the International Code Council Evaluation Service. This acceptance criteria validates the design capacity, installation procedures, and material standards that helical pile systems must demonstrate before they can be considered code-compliant. When we specify and install helical piers, adherence to AC358 is not optional — it is the foundation of a reliable, defensible engineering solution.

In Colorado, the need for AC358-validated systems is particularly acute. Our region’s expansive clay soils swell when wet, shrink when dry, and subject foundations to relentless stress year after year. Add in freeze-thaw cycles and aging Front Range building stock, and you have a recipe for settlement, heaving, and structural cracking that demands more than a one-size-fits-all fix. A pier system that has passed the ICC-ES AC358 standard carries independent, third-party verification that it can perform under these exact kinds of challenging geotechnical conditions.

As a family-owned and operated company since 1996, we have built our reputation on installing helical piers that meet the most current ICC-ES acceptance criteria. Every installation our team performs follows the design-verification, material-traceability, and torque-monitoring protocols that AC358 requires. That compliance does not guarantee a specific outcome — site conditions vary, and we always recommend consulting a licensed structural engineer for project-specific recommendations — but it does mean our clients receive a pier system whose performance characteristics have been methodically tested and documented. In an industry where shortcuts are tempting, we stand behind the discipline AC358 demands. The Experts in Steel Piers do not cut corners — we follow the code.

What ICC-ES AC358 Defines for Helical Foundation Systems

ICC-ES AC358 defines the acceptance criteria that helical foundation systems must meet for code compliance, establishing a rigorous framework for evaluating helical pile systems and devices. When contractors face foundation problems in the Colorado Front Range, adherence to AC358 ensures proper helical system design and reliable structural performance. According to the ICC Evaluation Service, these criteria provide a standardized method for assessing the structural adequacy and durability of helical foundation products before they are accepted for use in construction projects under building codes.

The ICC-ES AC358 criteria establish four primary requirement categories that govern helical foundation performance, and understanding each one is essential for engineers and contractors working with deep foundation systems, particularly when addressing foundation problems in the Colorado Front Range. The following comparison table outlines these requirement categories, their specifications, and the practical implications for field installation.

The table captures how AC358 bridges the gap between product evaluation and real-world application, ensuring that helical pile systems deliver predictable performance across varied site conditions. Each category addresses a critical aspect of foundation reliability, and together they form a comprehensive quality assurance framework that we follow in our installation practices.

Design Capacity Verification requires test piles or empirical methods as specified in AC358 section 4.2, and this process ensures that load-bearing capacity matches the design requirements for each specific project. The American Society of Civil Engineers (ASCE) deep foundation design guidelines reinforce this approach by emphasizing the importance of site-specific geotechnical evaluation rather than relying on generalized assumptions. Field verification through load testing provides the data necessary to confirm that installed helical piles will support the intended structural loads safely.

Corrosion Protection mandates minimum steel thickness, coatings, and galvanizing based on soil corrosivity categories, with varied protection levels specified for different environmental conditions. AC358 establishes clear thresholds for determining when additional protective measures are necessary, ensuring long-term durability in aggressive soil environments. We hot-dip galvanize pier components to meet these requirements, providing reliable bearing performance throughout the service life of the foundation.

Installation Torque Correlation defines the torque-to-capacity relationship per section 5.3, establishing a correlation factor derived from load tests that allows field verification of design capacity during installation. Monitoring installation torque provides immediate feedback on whether the helical pile has achieved the required bearing capacity. This real-time verification capability is a significant advantage of helical foundation systems, as it reduces uncertainty and allows adjustments during the installation process.

Material Standards reference ASTM A500 for structural tubing and ASTM F1554 for anchor bolts, specifying steel quality and fabrication requirements that ensure consistency and reliability in manufactured components. Quality assurance through material certificates provides documentation that the steel used in helical pile fabrication meets the specified standards. We install helical piers fabricated to ASTM standards, which supports the predictable performance that engineers and building officials expect from code-compliant foundation systems.

Adherence to ICC-ES AC358 is fundamental to reliable helical foundation systems, and these criteria provide the technical basis for designing and installing foundations that perform as intended. However, every project involves unique site conditions, soil characteristics, and structural requirements that demand professional engineering judgment. We recommend that property owners and contractors consult a licensed structural engineer for project-specific design recommendations and evaluation of foundation conditions.

Corrosion Protection, Soil Requirements, and Load Testing Under AC358

Building on the overview of ICC-ES AC358, this section examines the specific criteria governing helical pier systems. Professional designers and installers rely on three interconnected elements of the standard: soil classification methods, corrosion protection mandates, and load testing protocols. Understanding each component ensures that helical pier installations meet the demanding performance and durability expectations required by the ICC-ES standard. For property owners and contractors across the Denver metro and Front Range region, these AC358 criteria provide a consistent framework for evaluating system integrity and long-term reliability.

Soil Classification and Installation Criteria

The AC358 criteria define three distinct soil corrosivity categories: non-aggressive, aggressive, and extremely aggressive. These classifications directly influence material specifications and installation parameters for helical pier systems. Non-aggressive soils represent the baseline condition, with moderate pH levels and low concentrations of soluble salts. Aggressive soils present elevated corrosion potential due to factors like high chloride content or acidic conditions, while extremely aggressive soils demand the most stringent protective measures.

Soil classification under AC358 uses torque correlation to verify helical pier capacity. During installation, the rotational torque required to advance the helix plates is continuously recorded, and the measured torque correlates with the pier’s load-bearing capacity. This torque-to-capacity relationship allows qualified installers to confirm that the pier reaches competent bearing strata and achieves the required design capacity without relying solely on theoretical calculations. We apply these principles to every project, confirming that each helical pier installed across our service area performs predictably under load.

The design approach should also consider broader ASCE deep foundation design guidelines for helical piles, which complement AC358 by addressing variable soil conditions. These professional engineering guidelines provide additional context for pile behavior in layered soils, settlement analysis, and group effects that may influence overall foundation performance. By integrating both standards, structural engineers develop designs that account for site-specific subsurface conditions while maintaining compliance with established acceptance criteria.

Corrosion Protection Strategies for Varying Soil Types

Steel components embedded in aggressive soils require robust protection to maintain structural integrity over the design life of the foundation. The AC358 requirements establish clear thresholds for minimum steel thickness, coating systems, and supplementary protection measures based on the classified soil corrosivity. These specifications ensure that helical piers resist section loss over time, preserving the load path from structure to bearing stratum. Neglecting corrosion protection can lead to progressive deterioration, which we have seen undermine otherwise sound installations.

The following table summarizes the ICC-ES AC358 corrosion protection requirements across the three soil corrosivity categories.

For aggressive soils, AC358 mandates hot-dip galvanizing per ASTM A123, which bonds a thick zinc layer to the steel shaft and helix plates. The zinc coating provides both barrier protection and galvanic protection, meaning even if the coating is scratched, the surrounding zinc sacrifices itself to protect the underlying steel. In extremely aggressive environments, the standard calls for a minimum steel thickness of 0.5 inches plus an additional protective layer beyond the galvanizing, and cathodic protection is recommended to provide ongoing electrochemical defense against corrosion.

At Rocky Mountain Steel Piering, we hot-dip galvanize pier components to meet these AC358 requirements, and we select coating systems appropriate to the soil conditions encountered on each project. The upfront investment in proper corrosion protection prevents the kind of progressive structural damage that, as noted in our discussion of foundation cracks, can escalate from minor cracking to total foundation failure if left unaddressed.

Load Testing Protocols and Documentation

The AC358 standard specifies rigorous load testing procedures to verify that helical pier systems perform as designed under field conditions. These protocols establish uniform acceptance criteria, ensuring that test results are comparable and reliable regardless of the testing agency or project location. Proper documentation of load testing creates a verifiable record that the installation meets or exceeds the required design capacity.

The standardized AC358 load testing process follows a structured sequence:

• Test pile selection: A representative number of helical piers are designated as test piles based on site variability and total project scope, ensuring statistical confidence in the results.
• Incremental loading: The test pile is loaded in controlled increments, with each load step held for a specified duration to observe time-dependent settlement behavior.
• Creep monitoring: During each load hold, deflection readings are recorded to evaluate creep rate, which must remain below the acceptance threshold defined per AC358.
• Acceptance criteria: The test pile passes if the net settlement after unloading does not exceed the specified limit, and the creep rate at the design load remains within allowable bounds.
• Reporting documentation: A complete test report must include load-settlement curves, creep data, soil boring logs, pier configuration details, and the installer’s certification.

These load testing requirements ensure that helical pier installations deliver predictable capacities. At Rocky Mountain Steel Piering, we incorporate these protocols into our quality assurance process, verifying performance on-site rather than relying on assumptions. The resulting documentation provides engineers, building officials, and property owners with objective evidence of compliance with ICC-ES AC358 criteria.

Understanding these AC358 requirements is essential before evaluating how they apply to common helical pier design scenarios. Note: All information is for general informational purposes. Consult a licensed structural engineer for definitive design and compliance decisions.

Applying AC358 Compliance in Helical Pier Installations

As a family-owned and operated since 1996 foundation repair specialist, we understand that meeting ICC-ES AC358 requirements is fundamental to every helical pier project we undertake. Now that we understand the AC358 criteria, let’s apply them in the field through a structured three-phase approach that ensures predictable capacities and code-compliant installations from start to finish.

Pre-Installation Documentation and Engineering Review

Before any equipment arrives on site, the paperwork and engineering review must be complete. AC358 compliance begins with Sealed Design Calculations from a licensed structural engineer; we never start excavation without them. Our foundation repair case study in Greenwood Village demonstrates the documentation we assembled prior to installation: sealed engineering drawings, geotechnical reports confirming soil bearing characteristics, and pier specifications matched to the design loads.

We recommend collecting Mill Certificates for Steel from the helical pier manufacturer and reviewing them before delivery to confirm the shaft material, helix dimensions, and galvanizing meet the project specifications. For the Greenwood Village Town Hall project, our pre-installation review included verifying that the 1-1/2 inch rounded corner square steel shafts conformed to ASTM standards and that the specified 30-foot average depth aligned with the geotechnical findings. A structural engineer’s certification letter confirming the design complies with AC358 performance requirements should also be part of the submittal package. Consult a licensed structural engineer for project-specific design and compliance.

Three-stage helical pier compliance workflow diagram

Torque Correlation and Capacity Verification During Installation

Once the documentation is approved and materials are on site, our focus shifts to torque monitoring and real-time capacity verification. We use calibrated hydraulic torque heads to record Torque Logs at each pier location during installation, capturing the installation torque at regular depth intervals. This data is critical because AC358 acceptance criteria tie the measured installation torque directly to axial capacity through correlation factors derived from the geotechnical report.

We apply the project-specific correlation factor to convert the final installation torque to an estimated ultimate capacity, verifying on the spot that each pier meets or exceeds the design load. For a Denver residential repair where we installed six MacLean/Dixie HFS helical piles to depths of 25 to 30 feet, the torque readings confirmed that every pier achieved the required bearing before we proceeded to the next location. We recommend maintaining continuous torque records; if torque drops unexpectedly or fails to reach the target correlation value, we pause, assess the soil conditions, and consult the engineer before advancing further. This step-by-step approach keeps every installation aligned with AC358 performance requirements.

Post-Installation Inspection and Reporting

After the last pier reaches its design torque, the final phase of AC358 compliance involves thorough inspection and documentation. Load testing may be required by the building department or project specifications; if performed, we document the Load-Settlement Curve in a formal test report that demonstrates the pier’s behavior under applied load. In the Greenwood Village Town Hall project, post-installation measurements confirmed that the controlled lift successfully raised the settled corner approximately 1-3/4 inches, and the resulting report provided the municipality with clear evidence of compliance.

For final acceptance, we prepare a Signed Installation Report that includes torque logs, pier locations, as-built depths, and any load test data. Both our lead installer and the project engineer review and sign this report before we submit it to the building department for approval and retain a copy for warranty records. We recommend assembling all AC358 documentation into a single compliance package so the owner and code officials have a complete chain of evidence from design through final acceptance. With these compliance steps in place, you can see how our methods deliver predictable results.

The following checklist summarizes the key compliance steps.

Advanced Engineering Considerations for AC358 Compliance

In addressing foundation stability across the Front Range, our approach is guided by the rigorous ICC-ES AC358 standard. Applied to different project types, AC358 introduces specific engineering considerations that determine the appropriate repair or construction strategy.

New Construction Considerations

For new residential construction, full design-capacity verification under AC358 is required. This process ensures that every helical pier performs to its intended load capacity and is coordinated directly with the builder’s foundation plan, preventing conflicts before concrete is poured. We work alongside structural engineers to integrate these specifications seamlessly into the project from the ground up.

For new commercial construction, AC358 compliance must be included within the building permit set. The larger structural load ranges common in commercial builds demand more extensive testing and documentation. Our certified installers manage this process, applying the same rigorous standards used in all new construction projects across the Denver metro area.

Retrofit Foundation Repair

Retrofit projects introduce a distinct layer of complexity beyond new construction. The primary engineering task becomes a thorough existing load path analysis to understand how the structure currently bears weight. In retrofit projects, ignoring foundation issues can lead to serious structural problems; understanding the consequences of ignoring foundation cracks in Castle Rock is essential before proceeding with AC358 compliance. Our 2019 retrofit project in Greenwood Village demonstrated this process clearly, where we installed 1-3/4 inch helical piers to an average depth of 17 feet to stabilize a foundation suffering from lateral movement.

Beyond the analysis, common challenges revolve around access. Installation equipment often faces tight spaces and limited room to maneuver compared to an open new-construction site. Our installation techniques are adapted for these confined conditions while maintaining the full verification standards required by AC358, ensuring predictable capacities and immediate loading with minimal site impact.

Meeting these requirements is where our training and equipment make the difference. For a definitive analysis, consult a licensed structural engineer, but when you are ready to start, our certified installers are equipped to deliver superior performance. Ready to start your construction project? We bring 30 years of experience to every AC358-compliant installation.

Below, we answer common questions about how ICC-ES AC358 acceptance criteria apply to helical pier systems and our installation approach.

What is ICC-ES AC358?

ICC-ES AC358 is the acceptance criteria for helical pile systems, issued by the International Code Council Evaluation Service. It defines testing methods, performance standards, and evaluation requirements that confirm a product’s structural capability and durability.

Why is AC358 compliance important for helical pier systems?

Compliance with the AC358 acceptance criteria provides third-party validation that helical piers have been independently evaluated for load capacity and long-term reliability. This supports code acceptance and gives engineers predictable design values for foundation projects.

Does RMSsco install helical piers that meet AC358 requirements?

We install helical pier systems that align with the ICC-ES AC358 standard. Our trained crews follow manufacturer specifications and installation protocols referenced in evaluation reports, although each project must be verified against its specific site conditions.

How does AC358 compliance benefit my construction project?

Using AC358 compliant helical pier systems helps streamline plan review, satisfies common building code provisions, and provides documented capacity ratings. For project-specific design, consult your structural engineer, and reach out to our team to discuss how our experience can support your installation.

Building Long-Term Performance Through ICC-ES AC358 Compliance

ICC-ES AC358 acceptance criteria represent the definitive benchmark for helical pier design, testing, and installation — ensuring predictable capacities, long-term durability, and minimal site impact. As The Experts in Steel Piers, we, a family-owned and operated company since 1996, install only ICC-ES AC358 certified helical pier systems so every foundation repair we complete on Colorado’s Front Range delivers reliable, engineered performance. For true peace of mind, choose AC358-certified helical pier systems and let our team provide a custom solution backed by decades of proven experience.

Resources

• Explore Foundation Repair Options for Colorado Front Range
• Discover Helical Pier Repair Case Study in Greenwood Village
• Learn About Castle Rock Foundation Crack Consequences
• Find Expert Helical Pier Foundation Repair Services
• Learn About Greenwood Village Town Hall Foundation Repair
• Get a Contractor’s Guide to Foundation Issues and Solutions
• Discover Helical Pile Repair for Historic Denver Foundations
• Learn About ICC-ES AC358 Helical Pile Acceptance Criteria
• Find ASCE Deep Foundation Design Guidelines for Helical Systems