In Australia, a water mist system installed where the National Construction Code (NCC) calls for sprinklers is approved as a Performance Solution, not by following a deemed-to-satisfy recipe. AS 4587, the Australian water mist standard, says so itself: a system installed to it is not a deemed-to-satisfy alternative to a mandatory sprinkler system (AS 4587 explained). This article sets out how the Performance Solution route works under NCC 2025 and what a water mist case has to show.
How does the NCC allow compliance?
Under NCC 2025, compliance means meeting the Governing Requirements and the Performance Requirements. The Performance Requirements can be satisfied by a Performance Solution, a Deemed-to-Satisfy Solution, or a combination of the two (A2G1) (NCC 2025 Volume One, Part A2). The Deemed-to-Satisfy Provisions are the recipe; a Performance Solution is the engineered alternative.
Why is water mist not deemed-to-satisfy?
Where the Deemed-to-Satisfy Provisions call for a sprinkler system, Specification 17 names the systems that satisfy them: AS 2118.1, or in listed cases AS 2118.4, AS 2118.6, Specification 18 or FPA Australia's FPAA101D and FPAA101H systems (S17C2). NCC 2025 Volume One does not mention water mist or AS 4587 at all (NCC 2025 Volume One).
AS 4587 closes the question from its side. Its introduction states that a system installed to it does not provide a deemed-to-satisfy solution, and its scope says it gives no requirements or guidance for water mist systems to replace mandatory sprinkler systems (AS 4587:2020 preview). A design that uses water mist where sprinklers are required therefore departs from the Deemed-to-Satisfy Provisions and has to be justified as a Performance Solution.
What must a Performance Solution show?
A2G2 gives two ways to succeed: show compliance with all relevant Performance Requirements, or show that the solution is at least equivalent to the Deemed-to-Satisfy Provisions. The proponent identifies the relevant Performance Requirements, including those in other Sections or Parts that the solution affects, and shows compliance through one or more Assessment Methods:
- evidence of suitability under Part A5;
- a Verification Method, either one in the NCC or another accepted by the appropriate authority;
- Expert Judgement;
- comparison with the Deemed-to-Satisfy Provisions.
For water mist in place of required sprinklers, the equivalence route asks whether the mist system achieves at least what the Deemed-to-Satisfy sprinkler system would, for this building and its hazards.
What steps does A2G2 require?
Where a Performance Requirement is to be met by a Performance Solution, A2G2 makes four steps mandatory:
- prepare a performance-based design brief in consultation with the relevant stakeholders;
- carry out the analysis the brief proposes;
- evaluate the results against the acceptance criteria in the brief;
- prepare a final report that lists the Performance Requirements and Deemed-to-Satisfy Provisions addressed, identifies the Assessment Methods used, details the brief, analysis and evaluation, confirms that the Performance Requirements are met, and states any conditions or limitations.
For fire safety, the Australian Building Codes Board's Australian Fire Engineering Guidelines describe how the design brief and the fire engineering analysis are carried out.
What evidence does a water mist case need?
NCC 2025 Part A5 lists the documentary evidence that can show a material, product, form of construction or design meets a requirement: a CodeMark certificate, a Certificate of Accreditation, a certificate from a certification body, a report from an Accredited Testing Laboratory setting out the tests and their results, a certificate or report from a professional engineer or other appropriately qualified person, or another document such as a Product Technical Statement (A5G3) (NCC 2025 Volume One, Part A5).
AS 4587 adds its own expectation: water mist is an application-specific solution, and each application or occupancy has to be proven against standardised fire tests and component tests, shown in a report from the fire test laboratory. A water mist Performance Solution therefore rests on fire test evidence for the occupancy in question, read against the design fire and acceptance criteria in the design brief. What such evidence covers, and what a component certificate does not, is set out in system fire testing vs component certificates.
Which NCC edition applies?
NCC 2025 is the current edition. States and territories adopt it on their own dates and some vary the Governing Requirements; New South Wales, for example, has its own version of A2G2. Confirm the edition and any variations with the project's building certifier before the design brief is written.
Where Mistelix stands
Mistelix designs its water mist systems with reference to NFPA 750. Full-scale fire testing, FM Approval and UL listing are planned, and our live status against every standard we work to is in our approvals ledger.
Sources: ABCB, NCC 2025 Volume One, Part A2 (A2G1, A2G2) and Part A5 (A5G3); ABCB, NCC 2025 Volume One, Specification 17 (S17C2); Standards Australia, AS 4587:2020 preview, for the deemed-to-satisfy statement and the fire test expectation; ABCB, Australian Fire Engineering Guidelines.