When it comes to designing safe and efficient metal buildings, the engineering standards behind the scenes matter just as much as the materials themselves. If you have ever wondered why cold-formed st...
When it comes to designing safe and efficient metal buildings, the engineering standards behind the scenes matter just as much as the materials themselves. If you have ever wondered why cold-formed steel structures perform so reliably under heavy loads and demanding conditions, the answer often traces back to one foundational resource: the AISI cold-formed steel design manual.
Published by the American Iron and Steel Institute, this manual serves as the definitive guide for engineers, architects, and construction professionals working with cold-formed steel members. It outlines the specifications, load calculations, and design methodologies that ensure structural integrity across a wide range of applications.
In this tutorial, you will learn what the AISI cold-formed steel design manual actually contains, how it differs from other structural steel standards, and why following its guidelines is critical for any metal building project. Whether you are brushing up on your engineering knowledge or preparing to work more closely with design specifications, this breakdown will give you the practical understanding you need to apply these standards with confidence.
Cold-formed steel (CFS) is precisely defined by AISI S100-16, the North American Specification for the Design of Cold-Formed Steel Structural Members, as structural members shaped at room temperature from carbon or low-alloy steel sheet, strip, plate, or bar not more than 1 inch (25.4 mm) in thickness. Unlike processes that rely on heat to make steel malleable, cold-forming uses roll-forming equipment to bend and shape metallic-coated sheet steel into finished structural profiles at ambient temperature. The result is a family of lightweight, high-strength members including studs, joists, purlins, girts, hat channels, and truss components that appear throughout the residential and light commercial construction market.
Hot-rolled structural steel is processed at extreme temperatures, which allows mills to produce the heavier wide-flange sections (W-shapes, I-beams) commonly associated with red iron frame buildings and large commercial structures. These members are governed by an entirely separate design specification and follow a fundamentally different set of engineering rules. The 1-inch (25.4 mm) thickness limit established in AISI S100-16 serves as the formal dividing line between the two methodologies. For buyers comparing a carport or RV cover to a full red iron building kit, this boundary is practically significant; each structure type requires a different engineering approach, a different specification set, and different design software.
Cold-forming fundamentally alters how steel behaves under load. The manufacturing process introduces residual stresses, work hardening, and geometric imperfections that do not exist in hot-rolled members. These characteristics create unique failure modes, including local buckling, distortional buckling, and global buckling, that require specialized strength and stability calculations. Standard hot-rolled design methods simply do not account for thin-walled behavior, which is why the Cold-Formed Steel Engineers Institute emphasizes that CFS design remains a largely self-taught discipline even among licensed structural engineers.
In practical terms, the structures most familiar to metal building buyers, including carports, residential steel buildings, roof purlins, and wall framing systems, rely almost entirely on cold-formed members. Understanding which standard governs a given structure is the first step toward evaluating engineering quality, code compliance, and long-term performance.
At the center of every cold-formed steel structural project in North America sits a single governing document: AISI S100-16, North American Specification for the Design of Cold-Formed Steel Structural Members, 2016 Edition, Reaffirmed 2020. This specification serves as the authoritative standard for the United States, Canada, and Mexico, covering structural members cold-formed from carbon or low-alloy steel sheet, strip, plate, or bar up to 1 inch (25.4 mm) in thickness. Its reach extends across virtually every load-carrying CFS application in buildings and other structures, making it the foundational reference that engineers, designers, and building officials consult when verifying structural adequacy.
The specification itself, while authoritative, is not designed to be a standalone calculation tool. That is precisely why AISI publishes the companion Cold-Formed Steel Design Manual (2017 Edition), formally designated D100-17E. This two-volume set is engineered to be used in direct conjunction with S100-16, translating the specification's provisions into practical tables, examples, and reference data that engineers can apply directly during the design process. The electronic version is available through the official AISI store at $170.00, making it an accessible investment for any professional working regularly with cold-formed steel systems.
Volume 1 functions as the working engineer's toolkit. It contains dimensions and section properties for standard cold-formed steel shapes, giving designers the geometric and cross-sectional data needed for member selection. From there, beam design tables and column design tables provide pre-calculated capacity values for bending and axial compression scenarios, dramatically reducing repetitive calculations. The volume also includes connection design examples covering screws, welds, and bolts; supplementary design information addressing special conditions and edge cases; and a test method bibliography that links design provisions back to the physical testing procedures that validated them.
Volume 2 contains the complete text of AISI S100-16 alongside its official Commentary, which is arguably just as important as the specification itself. The Commentary explains the research basis, behavioral theory, and engineering rationale behind every provision in Volume 1's tables. Because CFS behavior differs significantly from hot-rolled steel, this explanatory layer is critical; the Cold-Formed Steel Engineers Institute notes that these concepts are rarely taught in standard engineering curricula, making the Commentary an essential self-teaching resource.
Rather than releasing an entirely new specification edition, AISI employs a reaffirmation and supplement process to keep S100-16 current. The 2020 reaffirmation incorporated both Supplement 1 and Supplement 2, updating specific provisions and clarifying application requirements where practice had evolved since the original 2016 publication. This means the operative version referenced in today's codes is S100-16 (2020), not the original 2016 release. Critically, the 2021 International Building Code formally adopted AISI S100-16 (2020) with Supplement 2, making these updates code-enforceable across every jurisdiction that has adopted the 2021 I-Codes. Practitioners must confirm they are referencing this reaffirmed version to ensure full code compliance.
The numbers tell a story that every practitioner should take seriously. The archived 2008 AISI Cold-Formed Steel Design Manual, housed in the Missouri University of Science and Technology Scholars' Mine repository, has accumulated 3,696 downloads and 5,343 abstract views since July 2018 despite being a superseded document. That sustained traffic is not a sign of casual curiosity; it reflects a real and measurable gap in awareness about which edition actually governs permitted work today. If you or your engineer are still referencing the 2008 manual for a current project, understanding why that creates a compliance problem is essential before breaking ground.
The 2017 Design Manual was not a minor refresh of its predecessor. AISI restructured the manual to align fully with the unified North American design framework, which means the 2017 edition integrates seamlessly with AISI S100-16 rather than the older S100-07 specification that underpinned the 2008 version. The updated edition introduced reliability-based design provisions calibrated to current probabilistic safety frameworks, revised connection capacity calculations to reflect more recent test data, and expanded coverage of the Direct Strength Method with new worked examples that the 2008 edition did not include. The two-volume structure of the 2017 manual places the full AISI S100-16 specification and its Commentary in Volume II, meaning the design reference and its governing standard are packaged together rather than treated as separate documents. These are not cosmetic changes; they represent substantive differences in how members, connections, and buckling behavior are analyzed.
The phrase "code-enforceable" carries specific legal weight that goes beyond professional best practice. AISI S100-16 (Reaffirmed 2020) with Supplement 2 is explicitly referenced in the 2021 International Building Code, which means that in every jurisdiction formally adopting the 2021 I-Codes, that standard carries the force of law. When a standard is incorporated by reference into a building code, designing to a superseded edition is not simply a technical shortfall; it constitutes a non-conformance that a plan reviewer can use to reject or delay a permit application. For builders and buyers purchasing steel structures, this distinction matters directly: a building permitted in a 2021 IBC jurisdiction must have structural calculations tied to the current enforceable standard, or the project faces tangible regulatory risk before a single fastener is installed.
The practical guidance is straightforward. If your structure is being permitted today under a jurisdiction that has adopted the 2021 IBC, the governing specification is AISI S100-16 (Reaffirmed 2020, with Supplement 2), and the design reference that supports it is the 2017 Cold-Formed Steel Design Manual. The 2008 edition is historically significant and clearly still in heavy circulation, but circulation does not equal compliance. Verify with your engineer that their calculations explicitly cite the correct edition, and confirm your building supplier's design documentation reflects the same standard before submission.
AISI S100-16 tells you whether a cold-formed steel member is strong enough. AISI S240-20, the North American Standard for Cold-Formed Steel Structural Framing, tells you how to build with it. Published in December 2020 and superseding the 2015 edition, S240-20 serves as the essential companion document addressing construction requirements common to both prescriptive and engineered design contexts. Its scope extends across all three NAFTA nations, making it the authoritative framing construction reference in the United States, Canada, and Mexico. A notable administrative change in this edition is that AISI S201-17, the North American Standard for Cold-Formed Steel Framing: Product Data, was absorbed directly into S240-20 and will no longer be maintained as a standalone document, reducing the number of separate references practitioners must manage on any given project.
The 2020 revision introduced several targeted but consequential updates that directly affect detailing practice in the field. For shear walls with height-to-length ratios greater than 2:1, Section B5.3.1 now requires designers to account for stud end moment resulting from joint fixity, a provision that previously went unaddressed in the standard. Screw edge distance requirements in Section B1.5.1.3.1 were revised to a specific value of 1.5 times the screw nominal diameter, giving connection detailers a clear quantified threshold to work from. Table A5-5 was expanded to include tracks with a flange width designation of 150, broadening the prescriptive product options available without requiring custom engineering solutions. Perhaps most practically significant for field personnel is the introduction of the Basic Frame Inspection concept in Chapter D, which establishes a structured quality-assurance tier specifically differentiated from general code inspections, giving authorities having jurisdiction a defined set of tasks to execute during construction review.
On a real project, AISI S100-16 governs every structural calculation: cross-section capacity, buckling behavior, and member-level strength checks for studs, joists, headers, and connections. Once the design is complete, S240-20 takes over, governing fabrication tolerances, connection detailing sequences, installation procedures, and inspection requirements. The 2020 edition was deliberately aligned to be consistent with AISI S100-16 with Supplement 2, meaning notation, chapter references, and material parameters coordinate directly between the two documents. An engineer stamping cold-formed steel framing drawings and a field inspector verifying compliance are, in effect, working from two halves of the same system.
The full AISI framing standards ecosystem extends well beyond S100 and S240. The S200-series addresses general cold-formed steel framing, with S220 covering nonstructural members. The S300-series governs floor and roof systems, including profiled steel diaphragm panel applications addressed in S310. The S400-series handles lateral design, covering seismic shear walls, strap-braced walls, special bolted moment frames, and diaphragms. AISI's most recent revision cycle updated six cold-formed steel design standards in total, including both S220 and S240, signaling a coordinated modernization effort across the full standards family rather than piecemeal revisions. Understanding how these cold-formed steel framing standards interrelate is essential for anyone working across multiple building systems on a single project.
All of these standards are now accessible through the ICC Digital Codes platform alongside the IBC and IRC, meaning engineers and permit officials can move between the 2024 IBC, its referenced AISI standards, and project-specific framing details within a single digital workflow. The 2024 I-Codes formally adopted AISI S100-16 (2020) with Supplement 2 alongside S240-20, embedding both documents into mainstream permitting practice. For jurisdictions that have adopted current I-Codes, referencing AISI S240 is not optional; it is a code requirement. Practitioners should verify their local jurisdiction's adopted code cycle, as state-level adoption of the 2024 IBC varies and some regions remain on earlier editions where S240-15 may still govern.
Carports, RV covers, sheds, barndominiums, and residential steel buildings all share a common structural foundation: light-gauge cold-formed steel members that fall squarely within the scope of AISI S100-16 and its companion framing standard, AISI S240-20. The defining threshold is material thickness. Any load-carrying steel member manufactured from sheet, strip, plate, or bar not more than 1 inch (25.4 mm) thick falls under AISI S100-16 jurisdiction, not the hot-rolled wide-flange specifications administered separately for heavier structural sections. The purlins, girts, C-studs, Z-sections, eave struts, and hat channels that form the skeleton of a carport or shed consistently fall well below that threshold, placing them firmly in cold-formed territory regardless of how the building is marketed or labeled.
The distinction between cold-formed and red iron (hot-rolled) construction is one of the most misunderstood points among metal building buyers. Red iron buildings use heavier I-beam and wide-flange primary frames governed by AISC specifications, while cold-formed carports, canopies, and many barndominium-style buildings rely on thin-gauge formed members for their structural work. However, many commercial and residential metal building systems are hybrid configurations: the primary frame may be hot-rolled structural steel while purlins, girts, and wall panels are cold-formed members fully subject to AISI S100-16. A barndominium with a red iron primary frame, for example, still depends on cold-formed secondary framing to transfer roof and wall loads to those primary members. Understanding which standard governs which component matters significantly when evaluating structural integrity, not just when reading a product specification sheet.
Both AISI S100-16 and AISI S240-20 carry explicit language that carries legal weight: application of these standards to any specific project must be reviewed by a registered professional engineer, and in most jurisdictions, that review is required by law before a building permit is issued. An engineer-stamped or PE-reviewed drawing set is the mechanism through which the general provisions of AISI S100-16 get properly translated into site-specific design conditions, accounting for local wind speed, ground snow load, seismic zone, and soil bearing capacity. This is not a bureaucratic formality; it is the codified process by which a generic standard becomes a structurally reliable building on a specific piece of land. As AISI standards are now integrated into the ICC Digital Codes platform alongside the IBC and IRC, building officials and plan reviewers access these requirements as part of their standard permitting workflow.
The full range of structures available through CarportX, including barndominiums, carports, RV covers, sheds, and steel buildings, incorporates cold-formed steel structural members that are subject to these design standards. Each product category relies on cold-formed purlins, girts, and framing components to carry real structural loads across real spans. The 2017 Cold-Formed Steel Design Manual introduced expanded design examples using the Direct Strength Method, a more efficient computational approach that accounts for actual cross-section behavior in the thin C-sections and Z-sections common to these product types.
For buyers comparing metal building options, the key takeaway is straightforward: structures designed to AISI S100-16 have passed through a codified engineering process that establishes a verifiable baseline of structural reliability. Non-engineered alternatives lack that traceable framework, and the difference becomes consequential when a structure faces a high-wind event, a heavy snow season, or a local building inspector with a permit requirement.
Buying a metal building online or over the phone introduces a fundamental challenge that does not exist when you walk a dealer's lot or visit a manufacturer in person: you cannot inspect the factory floor, review structural drawings face-to-face, or physically verify material quality before committing to a purchase. For most buyers, this gap creates legitimate uncertainty. Standards compliance fills that gap. When a supplier demonstrates that their structures are designed to AISI S100-16 (Reaffirmed 2020) and AISI S240-20, those citations are not marketing language; they are verifiable references to publicly available, code-adopted engineering standards that define exactly how the steel in your building must perform. Compliance with those standards is the clearest available proxy for structural quality and permitting reliability when you cannot verify either in person.
The PE review requirement built into the AISI and IBC framework deserves more attention than it typically receives in supplier conversations. Both AISI S100 and S240 explicitly state that application to any specific project must be reviewed by a registered professional engineer, and in most jurisdictions that requirement is mandated by law. The purpose is substantive, not administrative. A licensed PE who stamps a drawing set is making a legal attestation that the structure has been designed for the actual wind, snow, and seismic loads present at your specific site. That accountability has real consequences: a PE places their license on the line with every stamp.
For a remote buyer, the PE-stamped drawing package is the closest equivalent to an in-person inspection. It confirms that a qualified, accountable professional has reviewed the design before a single component is fabricated. One important distinction worth understanding: a site-specific PE-stamped drawing set is qualitatively different from a generic engineering letter. Many suppliers offer the latter as an add-on. Only the former gives your local building department the project-specific documentation needed to issue a permit efficiently.
The code adoption chain matters here in a practical way. As detailed by the Steel Framing Industry Association's codes and standards resource, AISI standards became the primary standards of record for cold-formed steel in the IBC beginning with the 2018 cycle. The 2021 IBC references AISI S100-16 (Reaffirmed 2020) and S240-20 directly, meaning structures designed to those editions speak the same language that most local plan reviewers are already using. A compliant drawing package reduces the likelihood of revision cycles, additional documentation requests, and permit delays because the engineering basis is already embedded in the code your jurisdiction enforces. Note that jurisdictions adopt IBC cycles at different times; confirming which edition your local building department uses is a practical first step before selecting a supplier.
Also worth noting: recent developments in cold-formed steel standards stewardship signal organizational changes in how these standards are maintained going forward. Buyers should confirm their supplier is actively tracking the current editions rather than working from superseded references.
Every remote buyer should be able to get clear, specific answers to these questions from any supplier they consider:
Which AISI edition governs your structural design? The correct answer references S100-16 (Reaffirmed 2020) and S240-20. A supplier citing the 2012 edition is working from superseded guidance.
Is a PE-stamped, site-specific drawing package included or available? Understand whether it is standard or an add-on, and confirm it is project-specific rather than generic.
Are the structures engineered for the wind, snow, and seismic loads at my site? Catalog designs not tailored to local conditions can fail permitting or, in a worst-case scenario, fail structurally.
Which IBC edition does your design package target? The answer should align with what your local jurisdiction has adopted.
CarportX brings over 80 years of combined industry experience in design consultation and project management, accumulated through the team's background and the company's foundation on Storage System Solutions' decade-plus of metal building market service. That depth of expertise means CarportX guides customers through every question above, from initial online inquiry to final purchase, providing the structural and regulatory context that buyers who are not engineers cannot reasonably be expected to navigate alone. Remote buying of AISI-compliant metal buildings does not have to feel like a leap of faith; with the right expert guidance, the standards framework makes the process transparent, verifiable, and straightforward.
The following reference table consolidates the four standards every metal building buyer, builder, and design professional needs to understand before submitting permit documents or ordering a structure.
Standard | Edition | Primary Scope | IBC 2021 Status | Access |
|---|---|---|---|---|
AISI S100-16 | 2016, Reaffirmed 2020 w/ Supplement 2 | Structural member design for CFS up to 1 in. thick | Directly referenced | Free download |
AISI S240-20 | 2020 | Structural framing assemblies: walls, floors, roofs | Companion via S100 pathway | Free download |
AISI S220-20 | 2020 | Nonstructural framing: partitions, soffits, furring | Companion via S100 pathway | Free download |
AISI D100-17E | 2017 | Design tables, section properties, worked examples | Not a code standard; engineering aid only | Paid, approx. $170.00 |
2008 Design Manual | 2008 (ARCHIVED) | Superseded reference, two code cycles out of date | Not recognized for current projects | Archived only |
AISI S100-16 is the only standard directly cited by name in the 2021 IBC. S240-20 and S220-20 enter the code compliance picture as companion documents referenced through the structural framing pathway, meaning they carry full code authority for their respective scopes but are not independently listed as primary IBC references. The 2017 Design Manual carries no code authority whatsoever; it is an engineering reference aid that compiles design tables and worked examples to simplify application of S100-16 in practice.
The governing standard shifts depending on the structural approach used in your specific building type. Cold-formed steel carports, sheds, and RV covers are designed under AISI S100-16 for individual member capacity, with AISI S240-20 governing the framing assembly. Barndominiums introduce both standards simultaneously, since the living space framing and the structural shell each require separate compliance paths. Red iron pre-engineered kits are the important exception: these structures use hot-rolled wide-flange sections governed by AISC 360, not AISI standards. The 1-inch thickness boundary in S100-16's scope is what draws that line, and buyers who conflate the two systems risk requesting the wrong engineering documentation for their permit application.
Practitioners who have not yet downloaded S100-16 and S240-20 from AISI's Build Using Steel educational platform should do so before beginning any design work. Both are available at no cost. Reserve the $170.00 investment in the 2017 Design Manual for projects where design tables and pre-worked column and beam examples will produce meaningful time savings. And if you encounter a reference to the 2008 manual anywhere in a supplier's documentation, treat it as a red flag that the paperwork has not been updated to reflect two full code cycles of revisions.
AISI S100-16 (Reaffirmed 2020) and the companion 2017 Design Manual represent the current governing framework for cold-formed steel structural design in the United States. Both documents are adopted into the 2021 International Building Code and are enforceable in most U.S. jurisdictions operating under that edition today. For anyone ordering a carport, barndominium, RV cover, shed, or red iron kit, this framework is not abstract. It is the baseline your local building department uses when reviewing submitted drawings.
The practical implication is straightforward: structures engineered to current AISI standards and delivered with a PE-stamped drawing package give buyers the strongest foundation for smooth local permitting, structural reliability, and long-term performance. A PE stamp confirms that a licensed professional engineer has reviewed load calculations, site-specific wind and snow conditions, and anchor bolt schedules against the same standards your Authority Having Jurisdiction enforces.
Navigating this documentation independently is demanding work that most buyers should not have to perform. CarportX combines 80-plus years of combined industry experience in design consultation, sales, and project management with a modern, transparent remote buying process. Every structure CarportX provides is properly engineered for your specific site conditions, so you receive code-compliant documentation without ever opening a standards manual yourself. Contact CarportX today to discuss AISI-compliant options built and sized for your project.
The AISI Cold-Formed Steel Design Manual is more than a technical reference; it is the backbone of safe, efficient, and code-compliant metal building design. By understanding its specifications, load calculation methods, and design methodologies, you give your projects a foundation built on proven engineering principles. Cold-formed steel structures perform reliably precisely because professionals follow these established guidelines rather than guessing at best practices.
Whether you are an engineer, architect, or building owner, taking the time to familiarize yourself with this manual pays dividends in structural confidence and long-term performance. Ready to put this knowledge into action? Download the latest edition of the AISI manual, consult with a qualified structural engineer, and apply these standards to your next metal building project. When you build with the right guidelines in hand, you build with lasting confidence.