AS/NZS 1170 Structural design actions: what builders need to know

TL;DR

AS/NZS 1170 is the suite of structural design actions standards that sets the load inputs every engineer uses to size your structure. For a standard Class 1a house under 8.5 m, the builder’s job is site-specific: confirm the wind classification (AS 4055 or AS/NZS 1170.2), check whether the site triggers specific earthquake design under AS 1170.4 Appendix A, and make sure the engineer’s details are stamped against the right edition. The NCC 2022 Volume Two Part H1 requires compliance with this suite; getting the wind region wrong at design stage is the most common structural hold at certifier.

In plain English

The AS/NZS 1170 series is a suite of five Australian/New Zealand Standards that define the design actions (forces, loads, and pressures) that structures must be designed to resist. Think of them as the inputs: the engineer’s drawings and structural details are the outputs. Without a verified load input, the structural members can’t be sized correctly.

For Australian residential builders, the suite underpins NCC 2022 Volume Two Part H1 Structure and the ABCB Housing Provisions Standard 2022 Part 2.2, which together govern the structural performance of Class 1 and 10 buildings. Whether you’re building a single-storey weatherboard or a two-storey brick veneer, the loads your engineer is designing against come from this series (verified 2026-05-08: ABCB, NCC 2022 Volume Two Part H1 Structure).

What it requires

The five parts

Part	Designation	Current edition	Scope
Part 0	AS/NZS 1170.0	2002 (Amdt 1-5)	General principles: limit states, load combinations, reliability
Part 1	AS/NZS 1170.1	2002 (Amdt 1-2, reconfirmed 2016)	Permanent (dead), imposed (live), liquid, ground and rainwater loads
Part 2	AS/NZS 1170.2	2021 (Amdt 1:2023)	Wind actions: wind speeds, regions, pressures
Part 3	AS/NZS 1170.3	2003 (Amdt 2:2017)	Snow and ice actions
Part 4	AS 1170.4	2007 (Amdt 2:2018)	Earthquake actions in Australia

(verified 2026-05-08: Standards Australia store, AS/NZS 1170 series)

Part 0: General principles (AS/NZS 1170.0:2002)

Provides the framework for using the rest of the series. Sets out:

Limit states: Ultimate Limit State (ULS, structural failure) and Serviceability Limit State (SLS, deflection, vibration). Engineers size members for both.
Load combinations: how to combine dead, live, wind, snow, and earthquake loads into design cases (e.g. 1.2G + 1.5Q, or 0.9G + Wu).
Importance levels: buildings are assigned an importance level (IL1 low hazard, IL2 standard housing, etc.) that determines the annual probability of exceedance used for wind and earthquake design.
Reliability: the underlying probability targets that make Australian structural design nationally consistent.

For a standard residential project, Part 0 runs in the background. The engineer applies it; the builder sees it indirectly through the structural design brief and engineer’s details.

Part 1: Permanent, imposed and other actions (AS/NZS 1170.1:2002)

Sets the dead and live load values used in structural calculations:

Permanent (dead) loads: self-weight of materials, finishes, fixed plant. Engineer uses known densities and areas.
Imposed (live) loads: occupancy loads, concentrated loads from people and furniture. For residential floors, the standard specifies minimum imposed loads per room type (e.g. habitable rooms, balconies).
Other loads: liquid pressure, groundwater, retained earth pressure, rainwater ponding.

For a residential builder, Part 1 is most relevant when a client wants heavier than standard finishes (concrete tiles, stone benchtops, heavy plant rooms) or when a deck or balcony is being added. These trigger a load review against Part 1 values.

Part 2: Wind actions (AS/NZS 1170.2:2021)

The most site-critical part for residential work in Australia. Sets out:

Wind regions: Australia is divided into regions based on wind hazard. The 2021 edition defines regions A0, A1, A2, A3, A4, A5, B1, B2, C and D (verified 2026-05-08: Wind regions AS/NZS 1170.2:2021, DomeShelter):

Region	Hazard	Typical locations
A0	Normal, low	Central Australia, arid interior
A1-A5	Normal	Most of southern and eastern Australia including capital cities
B1-B2	Intermediate	Northern NSW, SE QLD (Gold Coast, Brisbane corridor), Gladstone
C	Cyclonic	Northern QLD, WA north of Carnarvon, NT coast
D	Severe cyclonic	Pilbara coast WA

Design wind speed: calculated from the regional wind speed, site multipliers (terrain category, topography, shielding, height), and building shape factors.
Wind pressures: ultimate and serviceability limit state pressures on external and internal surfaces.

For residential builders, the practical output is the wind classification used in the structural documentation. For standard houses within the geometric limits of AS 4055:2021 (height under 8.5 m, width under 16 m, roof pitch under 35 degrees), the engineer or building designer typically uses AS 4055:2021 Wind loads for housing as the simplified alternative, which maps the AS/NZS 1170.2 wind regions into N1 to N6 and C1 to C4 wind classes (verified 2026-05-08: AS 4055:2021, Standards Australia store).

When the house falls outside AS 4055 geometric limits, AS/NZS 1170.2 applies directly and the engineer nominates a design wind speed.

Part 3: Snow and ice actions (AS/NZS 1170.3:2003)

Covers snow load on roofs and ice loads. Applies in alpine and sub-alpine areas of NSW, VIC, TAS, SA, and ACT. For most residential builders, this part is not relevant. It becomes material for:

Mountain resorts and alpine chalets
High-elevation areas in the Snowy Mountains, Victorian High Country, or Tasmania’s central plateau
Carport or verandah roofs in areas where snow accumulation is expected

If the site is in a snow region, the structural engineer’s brief must address Part 3. The certifier will ask for it.

Part 4: Earthquake actions (AS 1170.4:2007)

Sets the seismic hazard inputs for structural design. Australia has a low but non-trivial seismic hazard. The key provision for residential builders is Appendix A, which contains simplified provisions for domestic structures:

Class 1a or 1b buildings less than 8.5 m in height that comply with Appendix A do not require a specific earthquake structural design: designing for lateral wind forces per AS 1684 or AS 3700 is considered sufficient to also resist earthquake forces (verified 2026-05-08: Victorian Building Authority, Earthquake design and construction).
Buildings that fall outside Appendix A limits are designed as Importance Level 2 structures and need a dedicated seismic design.

In practice, most standard Australian housing satisfies Appendix A. The exception is areas with elevated seismic hazard (parts of WA, SA, and NSW) or unusual construction (unreinforced masonry, heavy tiled roofs on tall buildings). The engineer assesses this; the builder’s job is to make sure the engineer has been asked.

The current edition incorporates Amendment 2:2018, which updated hazard maps and established a minimum hazard design factor (verified 2026-05-08: Standards Australia, AS 1170.4:2007 Amd 2:2018).

What it doesn’t cover

Member sizing: the 1170 series gives the loads; AS 1684 (timber framing), AS 3700 (masonry), AS 4600 (cold-formed steel), and concrete standards size the members against those loads.
Geotechnical loads: soil investigation and footing design against reactive or expansive soils are governed by AS 2870 (residential slabs and footings), not AS 1170.
Bushfire loads: BAL (Bushfire Attack Level) structural and cladding requirements are governed by AS 3959, not the 1170 series.
Flood loads: site-specific flood assessment is a planning and engineering matter outside the 1170 suite.
Wind classification confirmation on site: AS/NZS 1170.2 and AS 4055 set the design framework. The actual wind classification for a specific site needs a desktop wind study or site assessment by the designer; the builder doesn’t determine it.

Practical implications

Know your wind region before you price

Wind region drives wind classification, which drives the structural specification and the cost of structural components (fixings, tie-downs, roof-to-wall connections, cyclone bolts). A site in wind region C or D will have significantly heavier structural requirements than region A. If you’re pricing a job in northern QLD, coastal WA, or the NT, confirm the wind classification before you lock in framing and roofing allowances. A wrong wind region discovered at certifier is a costly redesign (verified 2026-05-08: ABCB Housing Provisions Part 2.2).

Get the engineer’s details stamped against the current edition

AS/NZS 1170.2 was significantly revised in 2021 (superseding 2011). The 2021 edition refined the wind regions, particularly in SE QLD and northern NSW (B1/B2 split) and redefined A0 for central Australia. If you’re working from older engineer’s details or wind reports, confirm the edition. An AS/NZS 1170.2:2011 wind assessment may give a different wind class than the 2021 edition for the same site (verified 2026-05-08: New version of the Wind Actions Standard AS/NZS 1170.2, GSES).

Certifier checks for AS 1170 compliance

Under NCC 2022 Volume Two Part H1, the Performance Requirement H1P1 requires that structures withstand all reasonable actions including wind and earthquake. The DTS pathway (H1D5 to H1D7) references AS/NZS 1170.2 and AS 1170.4 directly. A certifier can require evidence that the AS 1170 load inputs have been correctly applied if the structural documentation is unclear or the site is in an elevated-hazard zone.

Importance Level and annual probability

Part 0 assigns residential buildings to Importance Level 2 (standard). The annual probability of exceedance used for design wind and earthquake events is fixed at this level. Most residential work will never need to think about IL1 (low hazard sheds) or IL3/IL4 (post-disaster critical infrastructure), but the concept matters if you’re designing farm storage, a community hall, or an emergency services facility alongside residential work.

Source link

AS/NZS 1170 series (paywalled): https://store.standards.org.au (search “AS 1170”)

NCC 2022 Volume Two Part H1 Structure (free, ABCB account required): https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/h-class-1-and-10-buildings/part-h1-structure

ABCB Housing Provisions Standard 2022 Part 2.2 (free download): https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/2-structure/part-22-structural-provisions

References

Australian Building Codes Board, NCC 2022 Volume Two, Part H1 Structure. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/h-class-1-and-10-buildings/part-h1-structure (verified 2026-05-08).
Australian Building Codes Board, ABCB Housing Provisions Standard 2022, Part 2.2 Structural provisions. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/2-structure/part-22-structural-provisions (verified 2026-05-08).
Standards Australia, AS/NZS 1170.2:2021 Amd 1:2023 Structural design actions, Part 2: Wind actions. https://store.standards.org.au/product/as-nzs-1170-2-2021-amd-1-2023 (verified 2026-05-08).
Standards Australia, AS 1170.4:2007 Amd 2:2018 Structural design actions, Part 4: Earthquake actions in Australia. https://store.standards.org.au/product/as-1170-4-2007-amd-2-2018 (verified 2026-05-08).
Standards Australia, AS 4055:2021 Amd 1:2024 Wind loads for housing. https://store.standards.org.au/product/as-4055-2021 (verified 2026-05-08).
Victorian Building Authority, Earthquake design and construction. https://www.vba.vic.gov.au/consumers/guides/earthquake-design-and-construction (verified 2026-05-08).

NCC structure: BCA, PCA, volumes and building classes, the NCC framework this suite feeds into
NCC 2022 Volume Two overview, Section H in detail, including H1 Structure
AS 3740, wet area waterproofing, a companion AS in the NCC DTS suite
AS/NZS 3000, the Wiring Rules, another major NCC-referenced AS
NCC bushfire BAL, bushfire cladding and construction requirements, a parallel structural consideration
NCC stairs and balustrades, another structural performance requirement in Vol Two