Our client's site assessment came back BAL-FZ. Is building even feasible at flame zone rating, and can a performance solution get us away from the deemed-to-satisfy requirements?

Yes, you can build at BAL-FZ, but not the way the question hopes. In NSW the deemed-to-satisfy route is closed at the flame zone, so a performance solution is the pathway itself, not a way of getting away from the prescriptive requirements. [1]

What BAL-FZ means. BAL-FZ is the top Bush Fire Attack Level: radiant heat flux exceeds 40 kW/m², with a significantly higher likelihood of flame contact from the fire front threatening building integrity and residents. [2] The flame zone is set by the calculated distance at which the radiant heat of the design fire exceeds 40 kW/m². [1]

Why the deemed-to-satisfy route is closed. The NCC references AS 3959 and the NASH Standard. The NSW variation to the NCC excludes both as a Deemed-to-Satisfy Solution for buildings required to be constructed to BAL-FZ. [1] But the Standard is still your starting point. Planning for Bush Fire Protection 2019 (PBP) says that although Chapter 9 of AS 3959 and the NASH Standard have not been adopted, they should still be used as a basis for a performance based solution showing compliance with the performance requirements of the NCC and PBP for construction in the flame zone. [1] That is the misconception to correct: a performance solution at BAL-FZ is not an escape from the detail. It is built on it, and it has to satisfy PBP as well as the NCC.

How a performance solution is put together. A Performance Solution must comply with all applicable Performance Requirements and be verified using one or a combination of four Assessment Methods: evidence of suitability, a Verification Method, Expert Judgement, and comparison with the Deemed-to-Satisfy Provisions. [3] [4] The code then sets the steps: [3]

• prepare a performance-based design brief in consultation with relevant stakeholders;
• carry out the analysis the brief proposes;
• evaluate the results against the brief's acceptance criteria; and
• prepare a final report covering the Performance Requirements identified, the Assessment Methods used, the steps taken, confirmation the requirement is met, and any conditions or limitations.

Any Verification Method used must be acceptable to the appropriate authority. [4]

The NSW points a flame zone brief must answer. PBP adds these from day one: [1]

• all flame zone developments should be sited and designed to minimise the risk of bush fire attack;
• flaming of significant elements, such as aesthetic wall cladding, is an unacceptable risk and will not be supported; only minor elements like address numbers, house names or decorative artwork may be considered, and only if they do not compromise the building's fire safety;
• fences and gates within 6 m of a building, or in areas of BAL-29 or greater, should be non-combustible only. At BAL-FZ that second limb always applies.

What is not covered here. The construction requirements for each BAL and the specific NCC bushfire Performance Requirement are not reproduced here. Consult AS 3959:2018 and an accredited bushfire consultant for materials and details, and confirm the Performance Requirements with your building surveyor.

Practical next step. The flame zone is set by distance from the hazard, so ask the consultant early whether siting changes could reduce the level. If not, get consultant, surveyor and designer around one design brief.

NSW edition note. NSW is on NCC 2022 (Amendment 2, in effect since 29 July 2025) until 30 April 2027, and NCC 2025 applies from 1 May 2027 with no election window. PBP 2019 refers to the NSW bushfire variation using earlier NCC clause numbering, so confirm the current clause reference with your surveyor.