What is the difference between DTS and Performance Solutions under the NCC?
Under Australia’s National Construction Code, there are two ways to comply with the Performance Requirements: a Deemed-to-Satisfy Solution or a Performance Solution. A Deemed-to-Satisfy Solution follows the prescriptive recipe in the NCC and is deemed to meet the Performance Requirement automatically. A Performance Solution demonstrates compliance through a tailored alternative using one or more recognised Assessment Methods, supported by evidence. Both pathways achieve the same Performance Requirement. The difference is how you get there. NCC 2025 has introduced new restrictions on Performance Solutions for structural reliability and combustibility.
How the NCC’s compliance structure works
The NCC is a performance-based code. The Performance Requirements at its core are the mandatory outcomes a building, plumbing system or drainage system must achieve. Compliance is achieved by complying with the Governing Requirements and the Performance Requirements (A2G1).
The Performance Requirements can be satisfied by a Performance Solution, a Deemed-to-Satisfy Solution, or a combination of the two. This is set out in A2G1 of NCC 2025 Volume One, and the corresponding provisions in Volumes Two and Three.
Deemed-to-Satisfy Provisions are the prescriptive pathway. They tell you what materials, components, design factors and construction methods to use. Use them and compliance is automatic.
Performance Solutions are the alternative pathway. They demonstrate compliance with the relevant Performance Requirements through one or more Assessment Methods. They enable innovation, complex projects, and design solutions the DTS provisions were not written to anticipate.
Deemed-to-Satisfy: the prescriptive recipe
A Deemed-to-Satisfy Solution is achieved by following the relevant Deemed-to-Satisfy Provisions in the NCC. The Provisions are prescriptive they tell you how, what and where things must be done.
Under A2G3, a Deemed-to-Satisfy Solution can show compliance through Evidence of Suitability in accordance with Part A5, or through Expert Judgement.
The advantage is certainty. The designer documents a DTS Solution, the certifier checks against the DTS clauses, and compliance is straightforward to demonstrate. The limitation is rigidity DTS does not always accommodate complex projects, heritage work, or performance-based design intent.
Performance Solutions and Assessment Methods
Under A2G2, a Performance Solution must be shown to comply with the relevant Performance Requirements through one or a combination of four Assessment Methods.
The first is Evidence of Suitability under Part A5, showing the material, product, form of construction or design meets the relevant Performance Requirement. The second is a Verification Method either a Verification Method provided in the NCC, or another Verification Method accepted by the appropriate authority. The third is Expert Judgement. The fourth is Comparison with the Deemed-to-Satisfy Provisions.
A Performance Solution must follow the prescribed steps under A2G2(4): prepare a performance-based design brief in consultation with relevant stakeholders, carry out the analysis proposed in that brief, evaluate the results against the acceptance criteria, and prepare a final report identifying all Performance Requirements addressed, all Assessment Methods used, and confirmation that the Performance Requirement has been met.
NCC 2025 changes: tighter rules for structural and fire safety Performance Solutions
NCC 2025 has introduced new restrictions on the use of Performance Solutions in two specific areas: structural reliability and combustibility.
A2G2(5) requires that where compliance with B1P1(2) (structural reliability) or H1P1(2) is proposed to be satisfied by a Performance Solution for specified materials listed in B1D4(a) to (f) or in the ABCB Housing Provisions, the Performance Solution must be achieved by demonstrating the solution is at least equivalent to the Deemed-to-Satisfy Provisions. In other words, for these specific structural materials, the Performance Solution pathway through Expert Judgement or other methods alone is no longer available — equivalence with DTS must be demonstrated. A2G2(5) takes effect one year after the adoption date of NCC 2025 in the relevant jurisdiction.
The Limitations clause under A2G2 also restricts the use of Expert Judgement as a standalone Assessment Method. Expert Judgement (A2G2(2)(c)) does not apply to a long list of Volume One Performance Requirements covering structural, fire safety, and access and egress (including B1P1(2), C1P1 through C1P9, D1P1 through D1P10, E1P1 through E1P6, E2P1, E2P2, E3P1 through E3P4, and E4P1 through E4P3) and Volume Two H1P1(2) to the extent it relates to structural or fire safety.
These changes reflect concerns about the consistency and rigour of Performance Solutions in safety-critical areas. They do not eliminate Performance Solutions in these areas they restrict the Assessment Method that can be used.
Combination solutions
A2G4 explicitly permits compliance through a combination of Performance Solutions and Deemed-to-Satisfy Solutions. Most complex Australian buildings fire-engineered commercial projects, heritage retention work, large mixed-use developments use both pathways across different elements.
Where a combination is used, A2G4(3) requires the designer to identify the relevant DTS Provisions of each Section or Part subject to the Performance Solution, identify the Performance Requirements from the same Sections or Parts relevant to those DTS Provisions, and identify Performance Requirements from other Sections or Parts that may be affected by the Performance Solution.
Responsibility boundaries
The designer is responsible for specifying the compliance pathway and producing documentation that supports it. The builder is responsible for installing to the specification. The certifier (appropriate authority) is responsible for being satisfied that the documentation demonstrates compliance and that construction matches the documentation.
When something is challenged, the documentation chain becomes the defence. Performance Solutions that are not documented to the standard required by A2G2(4) are a frequent cause of certification delays and disputes.
Common misconceptions
Performance Solutions are not a shortcut. They require more documentation, not less. A Performance Solution that is not properly documented and supported by evidence under an appropriate Assessment Method is a compliance failure.
Performance Solutions do not lower the performance standard. Both pathways achieve the same Performance Requirement. They differ in method, not in outcome.
Performance Solutions are not the architect’s or designer’s role alone. They typically involve fire engineers, building physicists, structural engineers, or other specialists depending on the Performance Requirement being addressed. The appropriate authority reviews the Performance Solution but does not author it.
Under NCC 2025, Performance Solutions for structural reliability and combustibility for specified materials must demonstrate equivalence with DTS. Expert Judgement alone is no longer available for a long list of structural and fire safety Performance Requirements.
Quick reference
Deemed-to-Satisfy Solution equals the prescriptive recipe follow the DTS Provisions and compliance is automatic (A2G3). Performance Solution equals a tailored alternative demonstrated through one or more Assessment Methods (A2G2). Combination solutions are permitted (A2G4). NCC 2025 restricts Performance Solutions for specified structural and fire safety provisions, requiring equivalence with DTS rather than Expert Judgement alone.
About CPD On Demand
CPD On Demand produces accredited Australian Continuing Professional Development courses on NCC compliance pathways, including detailed treatment of NCC 2025 Performance Solutions, Assessment Methods, and Evidence of Suitability. Courses are available for Architects and Building Designers, Builders and Project Managers, Building Surveyors and Certifiers, and Energy Assessors.