Steel Frames
Almost nobody outside the structural engineering world has heard of AS/NZS 4600, and yet it is the single standard doing the most work behind the scenes on every light gauge steel frame built in Australia. It sets the actual engineering rules for how thin, cold formed steel sections are allowed to be designed, and it sits quietly behind the National Construction Code every time a steel frame gets building approval. This guide explains what AS/NZS 4600 actually covers, how it connects to the residential specific NASH Standard most steel framed homes are really built to, and where it fits alongside the other standards that govern a project.
AS/NZS 4600, titled Cold-formed steel structures, sets out the minimum requirements for the design of structural members cold formed to shape from carbon or low alloy steel sheet, strip, plate or bar up to 25mm in thickness, used for load carrying purposes in buildings. The key word is cold formed. Steel framing used in residential and light commercial construction, the studs, tracks, joists and trusses that make up a typical light gauge frame, is manufactured by rolling or pressing thin steel sheet into shape at room temperature, rather than being cast or hot rolled the way heavier structural steel sections are. That manufacturing process behaves differently under load to a hot rolled section, which is exactly why cold formed steel needed, and got, its own dedicated design standard rather than being folded into the standard for heavier structural steel.
AS/NZS 4600 did not appear from nowhere. It originated in Australia as AS 1538 in 1974, was revised in 1988, and was jointly redeveloped with New Zealand and redesignated AS/NZS 4600 in 1996. It has been revised twice since, in 2005 and again in 2018, which is the current third edition still in force. Each revision has generally tightened and modernised the design rules as understanding of cold formed steel behaviour has improved and as the range of products on the Australian market has grown, including the higher strength G450, G500 and G550 grades now common in residential framing.
Here is the detail that actually matters to anyone building or buying a steel framed house rather than designing one from first principles: most homeowners and builders will never directly reference AS/NZS 4600 on a residential project. Instead, they will encounter the NASH Standard, Residential and Low-rise Steel Framing, published by the National Association of Steel-framed Housing, which takes the general engineering rules in AS/NZS 4600 and translates them into prescriptive, ready to use span tables, connection details and construction requirements specifically for houses and low rise buildings. Standards Australia formally acknowledges this relationship in AS/NZS 4600 itself, which includes permission from NASH to reproduce sections of its own residential framing standard, a sign of how closely the two documents are meant to work together rather than as separate, competing rule sets.
In practical terms, AS/NZS 4600 is the underlying engineering standard a structural engineer designs to when calculating member capacities, while the NASH Standard is what a builder, certifier or fabricator like CMC Steel Solutions is more likely to reference day to day for a typical residential wall, floor or roof framing job, since it packages the same engineering principles into a form built for houses specifically.
AS/NZS 4600 is a joint standard, developed and maintained by Standards Australia and Standards New Zealand together through committee BD-082, Cold-formed Steel Structures. Harmonising the two countries’ design rules into a single document means a steel frame designer, manufacturer, or product tested and certified in one country does not need an entirely separate set of design provisions to work to the other’s requirements, which keeps the supply chain and the certification process considerably simpler on both sides of the Tasman than maintaining two parallel standards ever could.
It is worth being precise about a distinction that gets blurred in general conversation. AS/NZS 4600 governs cold formed (light gauge) steel, the kind used in most residential and light commercial framing. Heavier, hot rolled structural steel sections, such as universal beams and columns used in larger commercial and industrial structures, are instead governed by AS 4100, Steel structures. A single project, particularly a larger commercial or industrial build, can genuinely use both standards on different parts of the same structure: AS 4100 for primary structural steel, and AS/NZS 4600 for light gauge wall and roof framing built off it. Knowing which standard applies to which part of a build is a basic but important piece of engineering literacy for anyone specifying steel framing.
Because AS/NZS 4600 has been revised several times, and because regulatory authorities can apply a new edition at a different time to when it is first published, two projects designed only a few years apart can technically be working to different editions of the same standard. This rarely causes practical problems on a new build, since a fabricator like CMC Steel Solutions designs to the current edition as standard, but it is a genuinely useful thing to understand if you are ever assessing an older steel framed structure, extending an existing one, or comparing engineering documentation between two different projects, since the specific edition referenced on a set of structural drawings is not just a formality, it reflects the actual design rules the frame was engineered against.
AS/NZS 4600 is a referenced standard within the National Construction Code, which means compliance with it is not optional best practice, it is how a steel framed building actually satisfies its structural performance requirements under the Code at the approval stage. This is the same mechanism by which the NASH Standard, AS 4100 for structural steel, and AS 1530.4 for fire resistance testing (covered in our separate guide to fire resistance of structural steel framing) all sit behind the Code rather than inside it directly.
Cold formed steel design does not happen in isolation from the rest of a project’s compliance requirements. A handful of related standards come up constantly alongside AS/NZS 4600 on a typical light gauge steel framing project, and understanding roughly what each one covers helps make sense of the paperwork that sits behind a compliant frame.
One of the more counterintuitive things AS/NZS 4600 accounts for is that a cold formed steel member’s strength is not purely a function of how thick the steel is. Base metal thickness, the actual thickness of the steel before any coating is applied, interacts with the section’s shape, its steel grade (commonly G450, G500 or G550 in residential framing, with the number referring to minimum yield strength in megapascals) and how the section is stiffened at its edges and flanges to resist local buckling under load. Two members of identical thickness but different profile shapes can have meaningfully different load capacities, which is precisely why AS/NZS 4600 spends so much of its content on section property calculation rather than simply prescribing a thickness for a given span. This is also why a steel frame’s design cannot be reliably eyeballed or substituted on site without going back to the engineering behind it, since changing a section profile changes its capacity in ways that are not always obvious from appearance alone.
On every project CMC Steel Solutions fabricates, the light gauge design work is carried out to AS/NZS 4600 and the NASH Standard together, with 3D BIM modelling used to confirm the design before fabrication begins. A reg 126 certificate and structural steel frame plan accompany the finished frame, giving a builder or certifier the documentation trail back to the standard the frame was actually designed and manufactured against. Understanding what AS/NZS 4600 covers does not change any of that process, but it does make the paperwork a lot less mysterious the next time it comes up in a certifier’s request or an engineer’s specification.
Key Takeaways
Standards Referenced Alongside AS/NZS 4600 on a Typical Project
Standard | What it governs | Relevance to steel framing |
AS/NZS 4600 | Design of cold formed (light gauge) steel structural members | The core design standard for wall, floor and roof framing |
NASH Standard, Part 1 and 2 | Residential and low rise steel framing, prescriptive span tables and details | The document most builders and certifiers reference day to day |
AS 4100 | Design of hot rolled structural steel | Applies to heavier structural steel, separate from light gauge framing |
AS/NZS 1170 | Structural design actions, including wind and general loads | Determines the loads a frame must be designed to carry |
AS 1397 | Steel sheet and strip, metallic coating classes | Governs the corrosion protection coating on the steel itself |
AS/NZS 1554 series | Structural steel welding | Applies where framing members are welded rather than screw fixed |
It is the Australian/New Zealand Standard titled Cold-formed steel structures, currently in its third edition, published in 2018. It sets the design requirements for structural steel members formed cold from thin steel sheet, strip, plate or bar.
No, though the two work closely together. AS/NZS 4600 is the underlying engineering design standard. The NASH Standard, published by the National Association of Steel-framed Housing, applies those engineering principles specifically to residential and low rise buildings in a more prescriptive, ready to use form.
Not typically. Heavier, hot rolled structural steel sections are generally governed by AS 4100, Steel structures. AS/NZS 4600 specifically covers cold formed, light gauge steel, the kind used in most residential and light commercial wall and roof framing.
Cold formed steel is shaped by rolling or pressing thin sheet at room temperature rather than being hot rolled or cast, which changes how the material behaves structurally, particularly around buckling and edge stiffening. AS/NZS 4600 accounts for these differences specifically.
Yes, in practice. AS/NZS 4600 is referenced within the National Construction Code, so meeting its requirements is part of how a steel framed structure satisfies building approval requirements, rather than being an optional benchmark.
Frames are designed to AS/NZS 4600 and the NASH Standard, confirmed using 3D BIM modelling before fabrication, and delivered with a reg 126 certificate and structural steel frame plan documenting the design.
AS/NZS 4600 is published and sold by Standards Australia and Standards New Zealand. Most builders and homeowners will get more practical, day to day value from the NASH Standard’s residential specific guidance, which our team can talk through in the context of a specific project.
If you are working through certifier or engineer requirements referencing AS/NZS 4600 or the NASH Standard, our team can walk through what it means in practice for your specific steel frame design.
Call CMC Steel Solutions on 1300 285 566, email info@cmcsteelsolutions.com.au, or contact us online to discuss your project.