What is a Group Number?
A woven wall or ceiling, whether a field of Cubic Pico's geometric relief along a hotel corridor or a run of framed panels in a school hall, has to satisfy the building certifier as well as the client, and the first fire question is its Group Number.
The National Construction Code (NCC) defines a Group Number as one of four groups of materials used to regulate fire hazard properties, applied to a finish, surface, lining or attachment to a wall or ceiling. The Australian Building Codes Board (ABCB) explains that the number, from 1 to 4, represents how readily a material ignites and releases heat: Group 1 materials perform best in a fire and Group 4 materials perform worst.
Standards Australia describes AS 5637.1:2015, the standard behind the number, as assessing wall and ceiling linings by their tendency to ignite, to release heat once ignited, to cause flashover and to release smoke, and by their contribution to fire growth.
A Group Number is a fire hazard property. Fire resistance is a separate property, which the NCC grades as a fire-resistance level in minutes for structural adequacy, integrity and insulation, and a Group Number describes how readily a material ignites and releases heat, rather than whether it can burn. The British Class 0 and Class 1 ratings and the US Class A rating belong to other systems; in the NCC, Class 1 is a building class, a dwelling such as a house.
How is a Group Number determined?
The ABCB describes two routes. The first is the full-scale room test to AS ISO 9705, which simulates a fire starting in the corner of a small room with one open doorway and records the time, if any, at which the heat release reaches 1 MW, the point the ABCB identifies as flashover. The second is the cone calorimeter test to AS/NZS 3837:1998, a small-scale test that measures a specimen's ignitability, heat release and smoke release under controlled radiant heat. The ABCB explains that, for some materials, the cone calorimeter data can be used to predict how the lining would perform in the room test, and that AS 5637.1 limits when that route may be used.
NCC 2025 clause S7C4(2) requires the Group Number of a wall or ceiling lining, and its smoke values, to be determined by an Accredited Testing Laboratory in accordance with AS 5637.1. A note to the clause says that, until the next edition of the NCC is adopted, the determination need not be made by an Accredited Testing Laboratory. Clause A5G6(3) then links a test to a product: a material is deemed to have a fire hazard property when it is identical with a tested prototype and a laboratory report confirms the result, or when it differs from the prototype in no more than a minor degree and a laboratory report confirms that it can achieve the property. So the sample in the report should match the fabric you specify.
What does the NCC require, and where?
Clause C2D11(1) applies NCC Specification 7 to the wall and ceiling linings of Class 2 to 9 buildings, and to attachments to internal walls and ceilings. Table S7C4 then sets the Groups permitted by building class, by whether the building is sprinklered, and by location: fire-isolated exits and fire control rooms, public corridors, specific areas (such as a hotel room, a classroom or an auditorium) and other areas.
The table shows the Groups a wall or ceiling fabric may have in the building classes most often fitted out with fabric.
Group Numbers allowed for wall and ceiling linings, NCC Table S7C4
NCC 2025 Volume One, Specification 7, Table S7C4: the Group Numbers permitted for wall (W) and ceiling (C) linings in the building classes these articles discuss. The rows are unchanged from NCC 2022. Read each row with the edition adopted in the project's state and the table notes.
"Sprinklered" means a building fitted with a sprinkler system complying with Specification 17, other than a FPAA101D or FPAA101H system (Table S7C4, note 1).
"Specific areas" (Table S7C4, note 2) are a sole-occupancy unit in a Class 2 or 3 building; an open-plan office (Class 5) or shop (Class 6) whose minimum floor dimension is more than five times its floor-to-ceiling height; a patient care area in a Class 9a health-care building; an auditorium in a Class 9b theatre or hall; a classroom in a Class 9b school; and a resident use area in a Class 9c building.
In a building that is not sprinklered, clause S7C4(1) also requires a smoke growth rate index of not more than 100 or an average specific extinction area of less than 250 m²/kg.
Whether a fabric wall panel or ceiling sail is a lining or an attachment is decided by the building certifier.
In a building without a sprinkler system complying with Specification 17, S7C4(1) adds a smoke condition: the lining must also have a smoke growth rate index of not more than 100, or an average specific extinction area below 250 m²/kg. For a house (a Class 1 building), ask your certifier.
The clause numbers and the Table S7C4 rows are the same in NCC 2022 and NCC 2025; NCC 2025 added the Accredited Testing Laboratory wording to S7C4(2). The edition in force depends on the state. NCC 2025 was adopted on 1 May 2026 in the Australian Capital Territory, Victoria and Western Australia, the ACT and Western Australia with 12-month transition periods. New South Wales, Queensland, South Australia and Tasmania adopt it on 1 May 2027 (Tasmania adopted it temporarily from 1 May to 4 June 2026), and the Northern Territory has not adopted it, so NCC 2022, adopted nationally from 1 May 2023, remains in force there.
Does a Group Number apply to a fabric wall panel or ceiling sail?
A fabric panel on a wall or a sail hung below a ceiling may be treated as a lining or as an attachment, and the building certifier decides which. The classification decides the clause: Table S7C2 refers wall and ceiling linings to S7C4 and its Group Numbers, and attachments to internal walls and ceilings to S7C7. Raise it with the certifier before the fabric for fabric wall panels or ceiling sails is chosen, and bring the Group Number and report for the exact fabric.
Which Acunic fabrics have a Group Number of 1 or 2?
Acunic is a range of woven textiles by Getzner Textil AG of Bludenz, Austria, most with a three-dimensional relief: Getzner describes the Cubic range by its geometric, three-dimensional structure, Optic by its three-dimensional surface texture, Accentric by its organic design language and Volumic as voluminous, and Basic as textured on both sides. Each has its own Group Number, as does Cubic Giga Dyed.
The table below gives the Group Number of each Acunic article from AKA Acoustics' Technical Product Summary (Version A, October 2024): Cubic Pico, Accentric Crash, Accentric Crinkle, Accentric Soundwave and Optic Braid are Group 1, and Cubic Giga, Cubic Giga Dyed, Cubic Mega, Optic Diamond, Optic Structure, Volumic Bubble, Volumic Square, Volumic Weave and Basic are Group 2.
Australian fire Group Numbers
Every Group Number in the table comes from AKA Acoustics' Technical Product Summary, from Cubic Pico, Accentric Crash and Optic Braid in Group 1 to Optic Structure in Group 2. Getzner's datasheets state that technical specifications may differ for dyed fabric, so for a dyed or printed order, ask AKA Acoustics about the evidence for the colour you choose.
Is Trevira CS a Group Number?
No. Every Acunic fabric is listed as "100% Polyester FR, Trevira CS", which describes the fibre: a permanently flame-retardant polyester from Indorama Ventures. The NCC asks for the Group Number of the lining, and the Technical Product Summary rates Cubic Pico Group 1 and Optic Structure Group 2, though both are woven from the same fibre. What Trevira CS is covers the fibre itself.
Getzner's datasheets also print B1, a German classification; in Australia, the fire rating is the Group Number.
What about curtains?
Curtains follow a different rule. NCC clause C2D11(3)(m)(i) exempts "a curtain, blind, or similar decor, other than a proscenium curtain required by Specification 32" from the fire hazard property requirements, and New South Wales adds a limit for curtains in public areas of entertainment venues. The exceptions and the New Zealand position are in do curtains need to be fire rated.
What should you ask a supplier for?
Ask for evidence that matches the fabric you will install:
- the Group Number for the exact fabric, and the document it comes from;
- the test report, with the laboratory, the standard (AS 5637.1:2015) and the test method (room test or cone calorimeter);
- the sample tested: its name, weight, thickness and colour, and the substrate it was mounted on;
- the smoke growth rate index or average specific extinction area, if the building is not sprinklered;
- a laboratory report if your colour, finish or construction differs from the tested sample (clause A5G6(3)).
AKA Acoustics gives each fabric's Group Number on its page in the collection and publishes the Technical Product Summary as a free download.
