Australia & NZ: AS/NZS 1170, AS 4100, AS/NZS 4600 and AS/NZS 5131

The joint AS/NZS framework

Australia and New Zealand share many structural standards, published jointly as AS/NZS, while keeping separate building codes and some country-specific standards. In Australia, the National Construction Code (NCC) – including the Building Code of Australia – sets performance requirements and references the AS/NZS 1170 loading series and the material design standards. NCC 2022 remains in force while states and territories adopt NCC 2025 on their own timetables from 2026 onward. In New Zealand, the Building Code clause B1 Structure is met through verification methods and acceptable solutions that cite AS/NZS 1170, NZS 1170.5 and NZS 3404, and building consent is issued by the local building consent authority.

Code mapping

Design points specific to this region

• Wind and cyclones. AS/NZS 1170.2:2021 defines wind regions including cyclonic regions C and D in northern Australia. Cladding and fixings in cyclonic regions must pass cyclic (low-high-low) testing under the NCC, and internal pressure from dominant openings is critical; see wind design.
• Earthquake. New Zealand has high seismic hazard and requires ductility-based design to NZS 1170.5 and NZS 3404; Australian seismic design to AS 1170.4 is usually less onerous for light PEBs.
• Steel grades. Plate is typically AS/NZS 3678 Grade 350 and cold-formed strip AS 1397 G450 or G550 with Z or AZ coatings.
• Durability. AS 4312 classifies atmospheric corrosivity, and AS/NZS 2312 guides paint and galvanizing selection.

Importance levels and design events

AS/NZS 1170.0 links the design loads to the consequence of failure through importance levels (IL1 to IL4) and the design working life. The importance level sets the annual probability of exceedance used for the ultimate wind, snow and earthquake events. For the common 50-year design working life the values are:

The NCC (Australia) and the NZ Building Code define which buildings fall into each level. Serviceability events are chosen separately – Appendix C of AS/NZS 1170.0 suggests criteria by element, and portal frame drift and purlin and girt deflection limits are normally agreed with the cladding supplier and the client; see serviceability and deflection limits.

AS/NZS 5131 construction categories and certification

AS/NZS 5131 governs fabrication and erection of structural steelwork and assigns each structure, or part of it, a Construction Category from CC1 to CC4, based on importance level, service category and fabrication category. Most industrial PEBs fall into CC2; CC3 applies to more demanding structures, for example those with higher importance levels or fatigue and seismic demands. The category sets requirements for weld inspection, traceability, tolerances and documentation. Each requirement is explained in our AS/NZS 5131 CC3 guide, starting with how the construction category is selected.

Clients and authorities increasingly require evidence that the fabricator is certified to AS/NZS 5131 at the appropriate category – in Australia commonly through the National Structural Steelwork Compliance Scheme, and in New Zealand through Steel Fabrication Certification (SFC) by Steel Construction New Zealand. Imported steel products are also expected to be verifiably compliant with AS/NZS material standards, for example through third-party product certification or test evidence.

World Steel in Australia and New Zealand

World Steel Construction holds AS/NZS 5131 Construction Category CC3 certification and fabricates under ISO 3834-2. WSC does not hold New Zealand SFC certification; where a New Zealand project requires SFC, the route must be agreed for that project. Designs are prepared to AS/NZS 1170, AS 4100 or NZS 3404, and AS/NZS 4600. See the global overview, European standards for comparison, market compliance and cold-formed steel.