AS/NZS 1170.1:2002 (R2018)
Structural Design Actions — Permanent, Imposed and Other Actions
AS/NZS 1170.1:2002 (Reconfirmed 2018) specifies the permanent (G) and imposed (Q) actions to be used with AS/NZS 1170.0 for the design of buildings and other structures. It tabulates uniformly distributed and concentrated imposed actions for occupancy categories (residential, office, retail, assembly, storage, parking, plant, roof access), specifies barrier and balustrade horizontal load requirements, and provides density values for common building materials used to derive permanent actions. The standard also includes liquid pressures, earth pressures, and miscellaneous imposed actions such as construction loads, machinery and crane loads, and impact loads. AS/NZS 1170.1 is the controlling reference for gravity actions on Australian and New Zealand buildings and is applied alongside AS/NZS 1170.0 (combinations), AS 1170.2 (wind), AS 1170.3 (snow and ice) and AS 1170.4 (earthquake). The standard is referenced by AS 3600 (concrete), AS 4100 (steel), AS 1720 (timber), AS 3700 (masonry) and AS 5100 (bridges) as the applicable gravity loading basis. It is reconfirmed as current; minor amendments have been issued covering specific occupancy categories and storage classifications.
AS 1170.1 is the standard most directly relevant to change-of-use and adaptive-reuse assessments — the projects where the imposed action on an existing structure changes because the occupancy or function of the space is changing. Three application points matter in the existing-asset context. First, occupancy categories drive the imposed Q value, and the choice of category is not always obvious for adaptive-reuse projects. The standard distinguishes office (3.0 kPa) from light retail (4.0 kPa) from storage (typically 5.0 kPa for general retail storage, with higher values for compact storage and warehousing). A heritage warehouse converted from storage to office reduces Q from 5.0 to 3.0 kPa, which can flip a previously inadequate slab to compliant — but only when the change of use is documented, occupancy controls are signed off, and the investigation file retains the engineering basis. The Victory Hotel post-fire reconstruction involved exactly this analysis: residential Q values applied to former commercial spaces required re-checking the floor systems against AS 3600 capacity. Second, the standard's barrier and balustrade horizontal load requirements (Table 3.3) are commonly under-applied on heritage and pre-2002 existing structures. Heritage buildings frequently have balustrade systems that pre-date the AS 1170.1 0.75 kN/m horizontal action for ordinary occupancy, or the 1.5 kN/m action for assembly use; physical pull-testing of suspect balustrades, or remediation to current standards, is often required for change-of-use approvals. Third, AS 1170.1 imposed-load reduction factors (Section 3.4) are routinely overlooked in existing-asset assessment. For column and wall design supporting multiple floors of standard occupancy, AS 1170.1 permits a tributary-area reduction (for slab and beam elements) and a multi-floor reduction (for columns and walls) reflecting the low probability that all floors carry simultaneous full imposed action. Applying these reductions to existing column capacity checks frequently demonstrates compliance that a non-reduced check would not, particularly in tall heritage office structures. The reductions are most meaningful at IL2 with category C office or D retail — the dominant occupancy types in Brisbane CBD heritage stock. The 12 Creek Street investigation applied imposed-action reductions to demonstrate column adequacy under the existing tenancy mix; without the reduction, conservative additions to column casings would have been recommended. The standard's permanent-action density tables (Appendix A) are also applied to derive G from measured cover and section thickness — TRSC takes physical measurements during investigation and checks them against AS 1170.1 default densities, because pre-1980 concrete frequently has lower measured density than current default values.
TRSC Form 15 certifications for change-of-use and adaptive-reuse projects always reference AS/NZS 1170.1 as the governing imposed-action standard. The Form 15 declaration is conditional on the structure meeting the design imposed action under the proposed occupancy. Where the proposed occupancy involves a higher Q than the original design, the Form 15 cannot be issued without either remediation, restriction of occupancy by signed agreement, or documented engineering basis for an alternative loading. Where occupancy reduction is the basis for compliance (e.g. converting storage to office), the Form 15 documentation includes the physical occupancy controls (signage, certified-area calculations, fit-out restrictions) that underpin the reduced loading. For column and wall capacity certifications using AS 1170.1 multi-floor reductions, the Form 15 file retains the tributary-area and floor-count calculations and the assumed floor-by-floor occupancy classifications, so the basis for reduction can be re-checked if occupancy changes in the future.