Every three years, the Australian Building Codes Board releases a new edition of the National Construction Code. Every three years, the industry reads the headlines, downloads the document, and files it away. Then projects proceed as they always have, and the compliance gaps accumulate quietly until an audit, a defect, or a dispute makes them impossible to ignore.

NCC 2025 is different. It contains changes that will directly affect how high-rise residential and commercial projects are designed, documented, and delivered in Australia. Not theoretical changes. Not definitional tweaks. Substantive amendments to the rules governing structural reliability, fire safety performance, water management, carpark sprinkler requirements, and building access that will require engineers, builders, and project managers to update their standard approaches.

This article analyses every major amendment in NCC 2025 Volume One that affects Class 2 to Class 9 high-rise construction — from a site engineer’s perspective. Not what the clauses say. What they mean.

Section A — The Structural Reliability Reckoning

The most significant governing change in NCC 2025 is the restriction placed on Performance Solutions for structural reliability and fire safety. Specifically, the amendment to A2G2 prohibits the use of Expert Judgement — clause A2G2(2)(c) — as a basis for Performance Solutions where those solutions relate to structural or fire safety Performance Requirements.

This is a fundamental shift. For years, Expert Judgement has been used as a flexible and relatively accessible pathway to justify non-standard structural and fire solutions. An experienced engineer provides a professional opinion, and that opinion forms the basis of the Performance Solution. NCC 2025 has closed that door for structural and fire safety — at least as a standalone pathway.

Alongside this, NCC 2025 adds a sub-clause to A2G2 requiring that Performance Solutions for structural reliability must be at least equivalent to outcomes achievable under the Deemed-to-Satisfy provisions. This sounds straightforward until you consider what it means in practice: the standard for structural Performance Solutions has just been anchored to DtS equivalence. You cannot argue for a lower reliability outcome on the basis of a more holistic risk analysis. The floor has been set explicitly.

The amendment to A4G1 introduces multiple changes permitting use of alternative referenced document editions where those editions appear on a register maintained by the ABCB. This is a genuine quality-of-life improvement for practitioners — it ends the frustrating situation where a current edition of AS 3600 or AS 1170 cannot be used because the NCC Schedule references an older version. The register framework allows for more responsive integration of updated standards. Projects should confirm which referenced document editions are on the register and plan their standard specifications accordingly.

The amendments to A5G6 introduce a new sub-clause specifying methods for determining combustibility, and new provisions allowing materials to be deemed to have a fire hazard property where they differ in a minor degree from a tested prototype — as confirmed by an Accredited Testing Laboratory. This is a practical change that addresses a long-standing documentation burden for material substitutions on site.

Section B — Structural Provisions Tightened

The structural provisions in Section B have undergone meaningful revision. B1P1 — the primary structural reliability Performance Requirement — has been amended to improve the robustness of Performance Solutions by requiring the use of B1V1 and appropriate allowances to demonstrate achievement of specific structural reliability levels. Transitional arrangements are included by way of a Note.

The deletion of B1P2 is a direct consequence of these B1P1 amendments. The former B1P2 covered glazing — its content has been effectively consolidated. Following Performance Requirements in Part B1 have been renumbered accordingly, which will require a complete review of any specification or design report that references old clause numbering.

B1V1 — the verification method for structural reliability — has been revised to incorporate component variability factors and specify further design actions. For engineers working on high-rise structures in Australia, this revision adds specificity to a verification pathway that was previously more broadly written. The intent is clear: structural Performance Solutions must be more rigorous, more defensible, and more explicitly tied to reliability targets.

The amendment to B1D2 deserves specific attention from high-rise structural engineers. The requirement now includes accommodation of 10-year deflection when designing structural substrates so that surface falls required by Part F1 are maintained. This is a direct recognition of the real-world problem that concrete slabs — particularly in podiums, balconies, and wet areas — deflect over time, and falls designed to the short-term elastic deflection may reverse or become inadequate within years of construction. The connection between long-term structural behaviour and hydraulic performance has been explicitly coded.

The revision to wind regions in B1D3 and S4C1 aligns with updated wind region mapping. This is not a minor administrative change — it affects design wind speeds in specific geographic areas and can materially affect structural design in affected regions. Projects in areas near wind region boundaries should confirm their design wind speed against the revised maps.

Section C — Fire Resistance: The Carpark Concession Ends

The fire resistance amendments in Section C contain one change that will affect the majority of high-rise residential developments in Australia: the removal of fire resistance concessions for open deck carparks that form part of multi-classified buildings.

Under NCC 2022, open deck carparks within multi-classified buildings — typically residential towers with podium carparks — received concessions under provisions S5C19, S5C22, and related clauses. These concessions recognised the natural ventilation characteristics of open deck carparks and provided relief from certain fire resistance requirements that would otherwise apply.

NCC 2025 removes these concessions unless the carpark is adequately sprinkler protected. The implication is significant: podium carparks in mixed-use or residential towers that are not sprinkler protected — and have previously relied on open deck concessions — will be subject to the full fire resistance requirements that apply to the building type and construction classification. For Type A buildings, these requirements are substantial.

Separately, NCC 2025 introduces a new provision — S5C11 — allowing the use of fire-protected steel in Type A construction in certain circumstances. This is a notable expansion of material options for high-rise structural engineers. Type A construction has traditionally required passive fire resistance through concrete encasement or intumescent coatings meeting specific standards. The new S5C11 provision provides a pathway for fire-protected steel where conditions are met, which may provide design flexibility particularly in long-span structural systems where concrete encasement adds significant weight.

The amendment to C1V3 requires that EW classification testing — used for external wall fire performance assessment — be undertaken by an Accredited Testing Laboratory. This follows the legislative and regulatory response to cladding non-compliance issues across Australia, and continues the trend toward stricter verification requirements for external wall fire performance. Project teams specifying external wall systems must confirm that testing evidence meets the Accredited Testing Laboratory requirement.

The smoke damper amendments — across S11C2, S11C3, and S11C4 — clarify smoke-proof wall specifications and remove the concession from smoke reservoir provision for doors serving zone pressurised fire compartments. High-rise residential buildings with zone pressurisation systems must review their smoke management design against the updated S11 specifications.

Section D — Access, Egress, and the Wayfinding Requirement

Section D introduces two changes that most high-rise project teams will need to address directly. The first is a new Performance Requirement. The second affects re-entry requirements across a broader range of building classes than previously covered.

New Performance Requirement D1P10 has been introduced to require the provision of wayfinding signage. This is a new obligation, not a clarification of an existing one. For high-rise buildings — particularly those with multiple towers, complex podium layouts, multiple tenancies, and extensive basement and carpark levels — wayfinding is a genuine safety issue. The legislative recognition of this in a Performance Requirement creates a new compliance obligation that must be addressed in both design documentation and construction delivery.

The corresponding Deemed-to-Satisfy provision, D3D31, requires the identification of stairways, floor levels, and sole-occupancy units through wayfinding signage. This provides the practical implementation pathway for D1P10. Building services and finishes teams should note that this is not signage in the generic sense — it is a specific wayfinding system covering vertical circulation elements and horizontal navigation within the building.

The amendment to D3D27 extends the re-entry provision to Class 2, 3, 6, and 7a buildings — enhancing requirements for re-entry from fire-isolated exits. This reflects the reality of modern mixed-use high-rise developments where multiple occupancy classes coexist in the same building, and occupants evacuating through fire stairs need to be able to re-enter the building at designated floors without relying on emergency services access.

The ramp concessions introduced through amendments to D1P2 and D3D22 provide some welcomed relief for accessibility compliance. Concessions have been introduced for step ramps, threshold ramps, and kerb ramps, along with associated handrail requirements. For Class 3 and Class 6 buildings — hotels and retail — these concessions have practical significance at building entries where grade changes are difficult to avoid and full ramp compliance has historically required significant engineering workarounds.

The addition of fire compartments served by horizontal exits to the scope of D2D8 is a clarification that will affect large footprint buildings — Class 5, 6, and 9b buildings in particular — where horizontal exits are used as part of the egress strategy.

Section E — Services and Equipment: Lifts, Sprinklers, and Carparks

Section E changes follow a consistent theme: the removal of concessions that have allowed certain building types to avoid requirements that apply to similar buildings, and the tightening of fire service infrastructure requirements.

The amendment to E1D9 removes the sprinkler concession for open deck carparks within multi-classified buildings. This is the Section E corollary of the Section C change discussed above. Under NCC 2022, open deck carparks within multi-classified buildings were exempt from automatic fire suppression system requirements in certain circumstances. NCC 2025 removes this exemption. Where carstackers are installed in fire compartments, sprinklers are now specifically required regardless of carpark deck configuration.

Small sized, low speed automatic lifts are no longer permitted under E3D7(1)(e). This removes a category of lift installation from the scope of permitted solutions and requires that lift installations in Class 2 to Class 9 buildings meet the full requirements of the applicable lift standards. For developers seeking to include lift access in smaller or boutique high-rise developments, this change removes a previously available cost-reduction pathway.

Section F — The Water Management Overhaul

Section F has undergone the most significant structural reorganisation of any section in NCC 2025. The water management provisions formerly contained in Part F3 have been entirely relocated and integrated into Part F1. Part F3 has been deleted. F1 has been extensively rewritten and renamed to accommodate these changes.

For high-rise engineers, the two new clauses are the most practically significant changes in the entire NCC 2025 update. F1D4 introduces a new explicit requirement for falls and drainage in concrete roofs, balconies, podiums, and similar elements. F1D5 specifies the construction requirements for these same elements. These are not new concepts — any competent engineer has been designing concrete roofs and balconies with drainage falls for decades. What has changed is that NCC 2025 now provides an explicit and enforceable Deemed-to-Satisfy requirement rather than relying on the general water management Performance Requirement.

The addition of F1D10, specifying surface finish requirements, is a companion provision to F1D4 and F1D5. Surface finish directly affects the maintainability and durability of drainage falls over time — a smooth surface delivers consistent drainage; a poorly finished surface collects standing water at low points that are not drains. The explicit surface finish requirement closes a gap that has caused defect disputes on numerous residential high-rise projects.

The rewriting of F1P1 to incorporate requirements previously in F1P2 and F1P3, and the relocation of F1P4 to F1P2, means that any specification, design report, or performance solution that references the old F1 clause numbering is now misreferenced. This is an administrative compliance risk that must be managed at the document review stage for projects adopting NCC 2025.

The sanitary facilities changes deserve specific mention. NCC 2025 amends F4D4 to permit all-gender sanitary facilities as a Deemed-to-Satisfy alternative to separate male and female facilities. This is a significant planning and design flexibility — for Class 5 commercial buildings, Class 6 retail, and particularly Class 3 serviced apartments, the ability to provide all-gender facilities under DtS rather than requiring a Performance Solution removes a documentation burden. The amendment to require additional closet pans for female patrons in Table F4D4i reflects contemporary usage data on sanitary facility demand.

The kitchen exhaust amendment — removing the word ‘commercial’ so that all kitchens meeting the equipment power threshold require exhaust hood systems — will affect residential high-rise projects with high-specification kitchen packages. Where kitchen appliances exceed the specified power threshold, an exhaust hood system is now required regardless of whether the kitchen is in a commercial or residential setting. Project managers specifying kitchen packages should confirm that their selections do not inadvertently trigger this requirement without corresponding exhaust provisions.

Section J — Energy Efficiency: Updated Targets

Section J amendments in NCC 2025 contain an important note: Class 2 buildings are referred back to NCC 2022 Amendment 2 for energy efficiency compliance. This means references to Class 2 buildings have been removed from Section J of NCC 2025 — a significant administrative detail for high-rise residential projects that must be confirmed with the project’s energy consultant at project inception.

J1P1 has been amended following project work to reflect updated performance targets. J1V1 has been revised to include further specifications for the energy model and align with these updated targets. For Class 3 to Class 9 buildings, the energy performance pathway has been updated and must be confirmed against the revised verification method requirements.

The removal of the ‘Design & As Built’ option from J1V2(1)(a) is a documentation change that affects how energy compliance is demonstrated at different project stages. Projects that have relied on this pathway should confirm their compliance documentation approach against the updated provision.

What NCC 2025 Means on the Construction Site

Reading NCC amendments as a designer is one thing. Living with them as a site engineer is another. Here is what NCC 2025 means for those who are actually building these projects.

The Five Highest-Risk Compliance Gaps in NCC 2025

Based on a review of all amendments, these are the areas most likely to generate compliance gaps on high-rise projects that continue with NCC 2022 design assumptions after NCC 2025 takes effect.

The Bigger Picture

NCC 2025 continues a directional trend that has been building since the Grenfell Tower fire in 2017 and accelerated through Australia’s own cladding non-compliance crisis. The direction is clear: the NCC is moving toward more rigorous verification, less reliance on subjective judgement, and more explicit performance requirements in areas where historical practice has produced building failures.

The prohibition on Expert Judgement for structural and fire Performance Solutions is the clearest expression of this direction. The requirement for Accredited Testing Laboratory confirmation of material fire hazard properties is another. The removal of open deck carpark concessions — concessions that existed partly because the fire risk of open deck carparks is genuinely lower, but also partly because they were commercially convenient — reflects a tightening of the risk tolerance embedded in the Code.

For engineers who build high-rise, this trend matters. The era of flexible interpretations, generous concessions, and performance solutions built on a single expert’s opinion is narrowing. Compliance is becoming more prescriptive, more verifiable, and more demanding of documentary evidence at every stage of design and construction.

The engineers who will thrive in this environment are those who understand the NCC not as a reference to be checked at DA stage and forgotten, but as a living compliance framework that shapes every decision from structural design through to operational handover. NCC 2025 is the latest update to that framework. It will not be the last.