NCC 2025 Explained: Moving Beyond “Expert Judgement” in Structural Engineering

If you are planning a new home or renovation, you may have seen headlines about Western Australia building regulations 2025 and the next National Construction Code (NCC) update. Building Ministers have agreed that NCC 2025 will be published by 1 February 2026, with jurisdictions able to consider adoption from 1 May 2026.

One of the proposed changes is less about new products and more about evidence. In its public comment draft, the Australian Building Codes Board (ABCB) proposes removing “Expert Judgement” as a stand-alone assessment method for structural Performance Solutions and introducing minimum reliability targets instead.

When homeowners are likely to notice

Many homes follow the Deemed-to-Satisfy pathway and move through approvals with few complications. Additional steps tend to appear when the structure is unusual, such as large openings, long spans, custom framing, steep or reactive sites, or retaining walls located close to the house.

These situations often require a Performance Solution. A Performance Solution is a tailored approach that still meets the NCC’s safety objectives, but it must be supported by appropriate evidence.

What “Expert Judgement” meant

Expert Judgement has been one accepted method for supporting some Performance Solutions. It relies on the opinion of a suitably qualified professional where testing or detailed calculation may not be practical.

The ABCB’s concern is consistency. Different experts can reasonably reach different conclusions on the same detail, which can lead to uncertainty, delays during certification, or requests for redesign.

What the draft proposes for structures

The draft structural package proposes two related changes. It introduces minimum reliability levels that must be achieved when a structural element is demonstrated through a Performance Solution, and it removes Expert Judgement as an assessment method for structural Performance Solutions (A2G2).

It also updates the structural verification method (B1V1 in Volume One and H1V1 in Volume Two), including how load combinations are applied. These changes form part of the broader NCC 2025 structural updates.

Reliability index

A reliability index is a single numerical measure that describes structural safety using probability. Higher values generally correspond to a lower likelihood of failure.

The ABCB notes that the proposed minimum targets were set by reviewing the reliability levels already achieved by commonly referenced NCC structural standards, then selecting minimum values within that established range.

What this means for Perth homes

In Perth residential structural engineering, many standard homes are expected to remain Deemed-to-Satisfy. For typical builds, owners may never encounter reliability targets directly.

For more complex homes, engineers may provide more detailed documentation. This can include stating the target reliability index, clearly listing assumptions, and documenting the load combinations used. Clearer evidence can make certification smoother and reduce late-stage changes.

For Perth residential builders, this may also affect timing. Structural decisions may need to be finalised earlier, before pricing and material orders are locked in.

Approvals and documentation in WA

In WA, building and plumbing legislation adopts the NCC as the primary technical standard. Once NCC 2025 is adopted, these requirements will flow through to approvals, records, and compliance processes.

This links directly to WA Building and Energy requirements. Thorough documentation is not just administrative. It provides clarity during construction and can be important later when selling or modifying the property.

A note on fire safety

The ABCB’s draft fire safety provisions also propose removing Expert Judgement as an assessment method for fire safety Performance Solutions. The draft notes that professionals can still apply judgement, but it must be presented through other assessment methods and supported by evidence.

What to ask before you sign

Ask: “Is any part of this home being assessed as a Performance Solution?” If the answer is yes, ask which elements are involved and what evidence will support them.

Then ask your builder how that evidence will be programmed and priced. Where additional checking is required, resolving it early is usually far more cost-effective than redesigning after contracts are signed.

Thinking about a renovation or custom build and want certainty before you lock in plans? Contact the Structural engineers in Perth WA at Complete Structural Design for clear advice, drawings, and inspections aligned with upcoming NCC changes. Visit completestructuraldesign.com.au.

Frequently Asked Questions

1. What is replacing Expert Judgement in NCC 2025?

   For structural Performance Solutions, the ABCB draft removes Expert Judgement (A2G2) and replaces it with minimum reliability targets. Designers must demonstrate compliance using calculations or verification methods that can be independently reviewed.
   

2. How to calculate structural reliability index for residential builds

   An engineer calculates a reliability index (β) using models of applied loads and material strength, then checks it against NCC minimum targets. The draft also updates B1V1/H1V1 to ensure consistent load combinations.
   

3. What’s the impact of NCC 2025 on Performance Solutions in Perth?

   If WA adopts NCC 2025, Performance Solutions will require clearer, auditable evidence. This can reduce disputes during certification, but complex homes may require more engineering input during the design stage.
   

4. Is Expert Judgement still allowed for fire safety in 2025?

   The ABCB draft removes Expert Judgement as an assessment method for fire safety Performance Solutions. Professional judgement still applies, but it must be demonstrated through other recognised methods and evidence pathways.
   

5. When will NCC 2025 apply in Perth?

   NCC 2025 is scheduled for publication by 1 February 2026. Jurisdictions may adopt it from 1 May 2026, with WA confirming its own commencement date and transition arrangements.