chalkline. Snap the line. Build to it.
regulation Compliance and regulation 5 min read

AS/NZS 1163 (Structural steel hollow sections): the spec under every post

AS/NZS 1163 is the product standard for cold-formed structural hollow sections in AU/NZ. Grades C350L0, C450L0. SHS, RHS, CHS. Posts, columns, portals.

By Dan Waring. Last updated 15 May 2026. Verified 15 May 2026.

Ask Chalkline about this →

In plain English

AS/NZS 1163, Cold-formed structural steel hollow sections, is the joint Australia/New Zealand product standard that defines what a “structural hollow section” actually is when one is called up on a drawing. It specifies the dimensional tolerances, the chemical composition, the mechanical properties (yield strength, tensile strength, impact toughness) and the mill-test certification required for square hollow sections (SHS), rectangular hollow sections (RHS) and circular hollow sections (CHS) supplied for structural use in AU and NZ. The current edition is AS/NZS 1163:2016 (verified 2026-05-15).

The standard does not say how a member is designed; that lives in AS 4100 (steel structures). AS/NZS 1163 says what the material has to be before AS 4100’s design rules apply. On a residential or small-commercial job, a builder reads “100x100x6 SHS Grade C350L0” or “150x100x5 RHS Grade C350L0” on the structural drawings; both citations are calling up AS/NZS 1163 product spec.

What it requires

For the steel mill and the supplier:

  1. Two grade designations. The standard recognises two structural grades in common use:
    • C350L0: minimum yield 350 MPa, minimum tensile 430 MPa, Charpy V-notch impact tested at 0 degrees Celsius (the “L0” suffix). The volume grade for residential and most commercial work.
    • C450L0: minimum yield 450 MPa, minimum tensile 500 MPa, also impact tested at 0 degrees Celsius. Higher-strength variant used where the engineer’s design calls for it; produced by selected mills.
  2. Section shapes. SHS (square), RHS (rectangular), CHS (round). Each section is designated by outside dimensions and wall thickness, e.g. 100x100x6 SHS is 100 mm square outside with 6 mm wall thickness.
  3. Dimensional tolerances. Cross-section dimensions, wall thickness, straightness, twist and squareness are all tolerance-controlled. Out-of-tolerance product fails the standard and cannot be supplied as compliant 1163 material.
  4. Mill certification. Every coil run must have a mill-test certificate (MTC) showing the cast analysis and mechanical test results that meet the grade. The fabricator and builder rely on the MTC to demonstrate AS/NZS 1163 conformance.

What it doesn’t cover

  • Design of hollow-section members. That sits under AS 4100. AS/NZS 1163 sets the material; AS 4100 sets how it is sized into beams and columns.
  • Hot-finished hollow sections. AS/NZS 1163 covers cold-formed sections only. Hot-finished hollow sections (rarely used in AU residential) sit under different European-aligned standards.
  • Welded fabrication and erection. That is AS/NZS 5131 (fabrication and erection) read with the AS/NZS 1554 welding series. AS/NZS 1163 stops at the supply gate.
  • Connection design or weld details. The hollow-section product spec does not specify how a 100x100 SHS connects to a UB or a concrete slab; that is the engineer’s connection design under AS 4100.

Practical implications

  • Substitution is a defect. A drawing calling “100x100x6 SHS C350L0” cannot be substituted with a 100x100x6 SHS of unknown grade, an imported section without AS/NZS 1163 certification, or a near-equivalent rolled section. Frame inspection routinely catches incorrect-grade SHS on portal posts.
  • MTC discipline is the supplier’s job and the builder’s check. On a Class 2 or bigger job under AS/NZS 5131 construction-category controls, mill-test certificates must be on file before the section is welded into the frame. On Class 1a residential the MTC discipline is lighter in practice, but the design under AS 4100 still assumes 1163 compliance.
  • Imported “near-1163” sections are common and risky. Cheap imported SHS without AS/NZS 1163 certification appears on building sites. The mill test, if any, is to a different standard with different chemistry and tolerances. The engineer’s design under AS 4100 has assumed 1163; an imported substitute is not the same material.
  • C450L0 is not a free upgrade. Substituting C450L0 for a designed C350L0 changes weld procedure requirements (under AS/NZS 1554) and may change buckling and stability behaviour at the connection. Where the engineer has designed for C350L0, supplying C450L0 is not a “better” outcome without re-design.
  • Mill rounding on wall thickness is a real risk. Cold-formed 1163 sections have a minimum wall thickness tolerance; nominal “5 mm” wall is the floor, not the average. Where wall thickness is critical (heavy point load, fatigue-sensitive), the engineer will specify a tighter tolerance or higher nominal thickness.

References

See also

Last updated: 2026-05-15. Verified: 2026-05-15. Quarterly review for currency.

Related articles