An AS 5637.1 group number tells you how much a wall or ceiling lining adds to fire growth in a room. It runs from Group 1, the best, to Group 4, the worst. The National Construction Code (NCC) then sets which group is allowed, based on the building class, where the lining sits and whether the building is sprinklered.
If you are specifying feature walls, lobby linings or ceiling panels, this is the number your certifier will ask for. This guide explains how the group is worked out, where the NCC calls for it, what results to look for, and the mistakes that hold up approval.
A group number is a fire hazard property, not a fire resistance level (FRL), and not a measure of combustibility. Keep those three ideas separate and most lining questions become simpler.
How an AS 5637.1 group number is worked out
AS 5637.1, Determination of fire hazard properties, Part 1: Wall and ceiling linings, sets out how a lining is given its group. There are two routes to a result.
- Full room test to AS ISO 9705. A room of 3.6 x 2.4 x 2.4 m is lined with the product. A gas burner in the corner runs at 100 kW, then steps up to 300 kW. The test records when, or whether, the room reaches flashover.
- Prediction from cone calorimeter data to AS/NZS 3837. Small specimens are tested for heat release, and the result is used to predict room behaviour.
The group follows from the time to flashover:
| Group | Room test result |
|---|---|
| 1 | No flashover within 20 minutes |
| 2 | Flashover between 10 and 20 minutes |
| 3 | Flashover between 2 and 10 minutes |
| 4 | Flashover within 2 minutes |
Flashover is the point where a room fire stops being local and the whole space ignites. A lining that delays it buys time for people to leave. That is why corridors and exits usually need a better group than a private room [verify].
Smoke is the second part of the result. In buildings without sprinklers, the NCC also limits smoke, using either a smoke growth rate index or a specific extinction area limit. A lining can reach Group 1 on flashover and still need its smoke value checked.
Where the NCC asks for a group number
In NCC 2022 Volume One, clause C2D11 and Specification 7 (fire hazard properties) set the group number required for wall and ceiling linings. The required group depends on three things:
- Building class. Each class of building has its own requirements, so confirm the class on the architectural drawings first.
- Location in the building. Exits and corridors used to escape generally need a better group than the rooms they serve [verify].
- Sprinkler protection. In unsprinklered buildings, the smoke limit applies as well as the group.
Check which edition of the NCC your state or territory has adopted before you rely on a clause number. Clause numbers can differ between editions, so quote the edition on your specification.
The practical sequence for a lining runs from the test report to the certifier. Each step is a place where a submission can stall.
Group results for ShapeShell™ lining materials
ShapeShift Technologies makes linings in three materials. Their fire results answer different questions, so read each line against the question it answers.
| Material | AS 5637 group | Other Australian results | European result |
|---|---|---|---|
| ShapeShell™-RT (fibre reinforced thermoset, FRP) | Group 1 | AS 1530.3, 7 mm panel: ignitability index 12, spread of flame index 0, heat evolved index 0, smoke developed index 6 | B-s2, d0 to EN 13501-1, 10 mm laminate |
| ShapeShell™-RC (glass fibre reinforced concrete, GRC) | Group 1 | Not deemed combustible to AS/NZS 1530.1; non-ignitable and flame resistant to AS/NZS 3837 | A2-s1, d0 to EN 13501-1 |
| ShapeShell™-RG (glass fibre reinforced gypsum, GRG) | Confirm per project | Confirm per project | Confirm per project |
Three points matter when you use this table.
Group 1 for ShapeShell™-RT is not a non-combustible rating. FRP is a thermoset composite and it burns. Its cone calorimeter results to AS 3837 show a peak heat release rate of 112.2 kW/m², a total heat released of 14.1 MJ/m² and sustained flaming at 51 seconds. The Group 1 result means a room lined with it did not reach flashover within the test. It says nothing about where a non-combustible material is required.
The tested product must match the installed product. A result belongs to the thickness, laminate, resin and finish that were tested. Our standard ShapeShell™-RT internal wall panels are 4 mm thick, while the results above were recorded on 7 mm and 10 mm specimens. Ask for the fire report that covers the panel you are installing, or a written assessment that extends it.
The system is assessed, not just the panel. Fire compliance looks at the complete wall or lining system, including the substrate, fixings, joints and coatings.
Choosing a lining material by location
The group number is one filter. The other fire questions, and the shape you want, narrow the choice further. Work through them in this order.
Start with combustibility. If the location, or the wall it sits on, needs a non-combustible material, a group number will not get an FRP lining through. ShapeShell™-RC is the material for those cases. It is glass fibre reinforced concrete, not deemed combustible to AS/NZS 1530.1, and it also gives a concrete look and mass.
Then check the group. Where the NCC asks for a group number and does not ask for a non-combustible material, ShapeShell™-RT can be considered at Group 1. This is where it is most useful: large panels, curved and free-form shapes, and wet or high-traffic areas where gypsum would not last.
Then think about weight and shape. Our standard ShapeShell™-RT internal wall panels are 0.6 m wide, up to 5.8 m long and 7.3 kg/m². That suits lift lobbies and tall feature walls fixed to a light frame. ShapeShell™-RG is our default for painted interior work and is about 30% lighter than GFRC. Confirm its fire results for each project before it is specified in a location with a group requirement.
Finally, check the finish. Colour, coating and texture are part of the tested product. Choose the finish early and check it against the report.
Wall lining fire rating checklist for specifiers
Use this list when you write the lining clause or review a supplier submission.
- Record the building class, the NCC edition and whether the building is sprinklered.
- Mark each lining location on plan: rooms, corridors, exits, lobbies and ceilings.
- Note the group number and any smoke limit required at each location.
- Ask for the AS 5637.1 report, not a summary sheet. Check the test route (room test or cone prediction) and the laboratory.
- Check that the tested thickness, resin, laminate and finish match the panel being supplied.
- Check the smoke result where the building is unsprinklered.
- Confirm site-applied paint or topcoats are covered by the report, or get them assessed.
- Keep the group number separate from FRL and combustibility requirements, and answer each one on its own.
- Put the report, the product description and the installed build-up in the certifier’s submission together.
Common mistakes with NCC group numbers
Treating Group 1 as non-combustible. A group number describes fire growth in a lined room. Non-combustibility is a separate test to AS/NZS 1530.1. A Group 1 FRP lining is still a combustible material, and it cannot be used where the NCC requires a non-combustible one.
Confusing a group number with an FRL. An FRL measures how long an element resists fire passing through it. A group number measures how a surface behaves in a room fire. A lining can have a good group and no FRL at all.
Submitting an overseas result. EN 13501-1 and ASTM results are useful for international projects. They are not an AS 5637.1 group number, and a certifier working to the deemed-to-satisfy provisions will usually ask for the Australian result [verify]. Where only overseas data exists, a performance solution may be the route.
Using a report for a different product. A 10 mm laminate result does not automatically cover a 4 mm panel, a different resin or a new coating. Small changes can move the result.
Forgetting the smoke limit. In an unsprinklered building, the group number alone is not enough. Check the smoke value too.
Leaving it to the end. Linings are often chosen late, after the fire engineer has finished. Bring the group requirement into the design brief, so the material choice and the panel thickness are settled together.
Next step
If you are choosing a lining for a corridor, lobby or ceiling, send us the drawings and the fire engineering brief. ShapeShift Technologies will review the panel, the fixing and the fire results against the locations you need to cover, and tell you which reports apply. Send drawings for a panel and fixing review.
