PCD 2025 - Improving structural Performance Solutions

We are proposing changes to Volume One and Two of the NCC to improve the robustness of Performance Solutions for structural components of buildings.

The changes include: 

• New minimum levels of reliability which must be achieved when demonstrating compliance of structural components through a Performance Solution (B1P1(2) in Volume One and H1P1(2) in Volume Two).
• Absorbing Performance Requirement B1P2 into new Performance Requirement B1P1(4) in Volume One for structural resistance. 
• Amending the Structural Reliability Verification Method to account for combinations of actions, rather than only individual actions (B1V1 in Volume One and H1V1 in Volume Two). 
• Removing Expert Judgement as an Assessment Method for structural Performance Solutions (A2G2).

More detail on the proposed changes to NCC Part B are in Table 1 and Table 2. Review the Structure examples calculations demonstrating the main steps to determine the level of reliability of structural components, using the proposed NCC 2025 B1V1 method.

Performance-based NCC

The National Construction Code (NCC) is a performance-based code containing Performance Requirements. To comply with the NCC, a solution must achieve compliance with the Governing Requirements and the Performance Requirements, which are the mandatory requirements of the NCC.

Practitioners can develop Performance Solutions to meet the Performance Requirements of the Code. This allows them to determine the most effective and innovative way to demonstrate compliance for their particular building.

We are working to increase the competent use of the Performance Requirements to support industry innovation. Quantification is one of the components to this initiative. Rigorously quantifying the Performance Requirements will provide objective levels of Performance for practitioners to target. This will encourage both increased use of Performance and competency when practitioners develop Performance Solutions. This will also help ensure a level playing field and reduce the risk of misinterpretation.

Related to this, many stakeholders have expressed a desire to reduce subjectivity and increase robustness in safety-critical areas such as structural safety, to ensure the desired level of public safety is achieved. 

Structural quantification framework

As part of our ongoing work to quantify the Performance Requirements, we propose introducing a new structural quantification framework for the next edition of the NCC. This framework is primarily focused on setting minimum performance levels for components made of new and innovative materials as well as alternative forms of construction.

This will enhance practitioner’s confidence that the Performance Solutions they develop meet the minimum requirements of the NCC. 

Expert Judgement

Expert Judgement is an NCC Assessment Method that allows the judgement of an expert (someone that has relevant qualifications and experience) to determine whether a Performance Solution complies with the Performance Requirements. What is defined as an expert for the purposes of this Assessment Method may differ between jurisdictions (e.g. airports and national parks).

To increase the robustness of building solutions in safety-critical areas, such as structural safety, and reduce subjectivity, we are proposing to remove the Expert Judgement Assessment Method in Part A of the NCC to demonstrate compliance for structural safety Performance Solutions. 

The aim is to prevent practitioners from setting levels of public safety solely at their own discretion and this will help produce more robust outcomes, leading to improved occupant safety.

The Expert Judgement Assessment Method will remain available for Performance Solutions to other parts of the NCC, which remain unaffected.

We have collaborated with key stakeholders and academics to determine the best way to quantify the Performance Requirements and improve structural Performance Solutions. 

The structural Performance Requirements in Part B1 of Volume One and Part H1 of Volume Two have been quantified in terms of a reliability index for individual components. This gives a relative measure of confidence that the structural component will perform its function in a satisfactory manner. 

The reliability index values have been derived from analysis of existing NCC referenced structural design standards for steel, concrete, timber, masonry and cold-formed steel. Each of these standards deliver slightly different reliability indices for different components and failure characteristics. The minimum values which have been included in the NCC are set to a level within the range of typical values across the referenced standards, to include the most common outcomes. These values are proposed to form the minimum requirements of the NCC.

We consulted with members of our peak technical committee, academic institutions, the Building Codes Committee (BCC) and the following key stakeholders:

• Engineers Australia (EA)
• Consult Australia (CA)
• Australian Institute of Building Surveyors (AIBS)
• Australian Institute of Architects (AIA)
• Building Products Industry Council (BPIC)
• Standards Australia committee representatives 
• Master Builders Australia (MBA)
• Property Council of Australia (PCA)
• Insurance Council of Australia (ICA)

Practitioners undertaking structural Performance Solutions will need to utilise the quantification framework to demonstrate compliance with the Performance Requirements. The existing Deemed-to-Satisfy (DTS) Provisions that are based on the Australian Standards for structural design are likely to remain the preferred option for components made of masonry, concrete, steel, composite steel and concrete, aluminium and timber.

Practitioners undertaking Performance Solutions for structural components will no longer be able to use the Expert Judgement Assessment Method. It means practitioners must use the quantification approach to set reliability indices. However, it will not prevent practitioners from applying their own professional judgement, which remains feasible under other Assessment Methods or when using Evidence of Suitability outlined in Part A5 where appropriate.

These amendments will improve the robustness of Performance Solutions and will give users of the NCC greater certainty they are meeting the Performance Requirements.

We've proposed similar changes to improve fire safety Performance Solutions.

• Understanding the NCC Assessment Methods
• Increased and competent use of performance
• Structure examples calculations

To read the full details of the changes, please review the NCC 2025 Volumes One, Two, the Housing Provisions Standard PCD and Section A.

Responses to the Public Comment Draft are invited until 11:59 PM AEST Monday 1 July 2024.

In line with the ABCB's process for undertaking public consultation, comment will only be accepted through the ABCB's online Consultation Hub.

To access the Public Comment Draft and response form:

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