Fibre Reinforced Facade Encyclopedia: Testing and standards
A wall lining is the internal surface material applied to a wall or ceiling inside a building, from plasterboard and timber panelling to decorative composite and cast gypsum systems. Unlike external cladding, internal linings are not regulated on non-combustibility under the National Construction Code. They are regulated on group number, a classification from 1 to 4 derived from how quickly a lining drives a room towards flashover.
Two different regimes govern the two faces of the same wall. The outside of a Type A building must be non-combustible. The inside must achieve a group number. A product that satisfies one has said nothing about the other.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Code reference | NCC 2022 Volume One Specification 7 Fire hazard properties | Check the edition adopted in your jurisdiction |
| Classification | Group number 1, 2, 3 or 4 | Group 1 is the best; Group 4 is not permitted in regulated locations |
| Classification standard | AS 5637.1 | From AS ISO 9705 room test or AS/NZS 3837 cone calorimeter data |
| Fire isolated exits | Most demanding location; Group 1 typically required | Varies with class and sprinkler protection |
| Public corridors | Group 1 or 2 typically required | |
| Other rooms | Group 1, 2 or 3 typically permitted | |
| Sprinkler effect | Sprinkler protection generally relaxes the group required | |
| Smoke criterion | Smoke growth rate index limit applies in certain classes | SMOGRA-RC, from the room corner test |
| Floor coverings | Regulated separately on critical radiant flux | AS ISO 9239.1, not group number |
Why linings are regulated differently
The fire risk a lining presents is not that it might burn in a furnace, but that it might accelerate a room fire to flashover before the occupants get out. That is a rate question, not a material question, and it is answered by a test that measures how much energy the lining adds to a growing fire. AS 5637.1 classifies linings into four groups on exactly that basis: Group 1 does not take the test room to flashover at all within twenty minutes, Group 2 does so only under the higher 300 kW burner exposure, Group 3 under the initial 100 kW exposure, and Group 4 within the first two minutes.
NCC Specification 7 then sets the group required by building class, by whether the building is sprinkler protected and by where in the building the lining is. Fire isolated exits and stairs are the most demanding, because they are the escape route; public corridors are next; rooms within sole occupancy units and general spaces are the least demanding. Certain classes also carry a limit on the smoke growth rate index from the same room test, so a group number alone does not always complete the assessment.
This system replaced the older AS 1530.3 early fire hazard indices for lining purposes. Those indices, including the ignitability index and the spread of flame index, are still produced and still appear in Specification 7 for materials outside the lining provisions, but a group number is what a lining submission needs.
What counts as a lining
The provisions reach wall and ceiling linings, and they apply to the finished surface as it will be installed, including its substrate, its adhesive or fixing method and any coating. A decorative panel bonded to plasterboard is not the same specimen as the same panel screwed to a steel frame over a cavity, and the classification report states the tested build-up. Attachments such as skirtings, architraves and trims are treated separately and generally attract limits on the proportion of the wall area they may occupy.
Floor coverings are outside this system. They are regulated on critical radiant flux measured to AS ISO 9239.1, which asks how far a flame front will travel across a horizontal surface under a radiant panel. Air handling ductwork, insulation and sarking each have their own provisions in Specification 7.
How a lining gets classified
Two routes lead to a group number. The full-scale route is the AS ISO 9705 room corner test, in which a real room is lined with the product and burned. The predictive route uses heat release data from the AS/NZS 3837 cone calorimeter, a bench test on a 100 mm square specimen, processed through the correlation in AS 5637.1. The cone route is faster and cheaper and is how most products are first classified; the room test is the reference method and governs where the two disagree.
Whichever route is used, the classification belongs to the specimen tested and the report should be read for the substrate, the thickness, the fixing method and any surface coating. Ask for the full report from an accredited testing body rather than a summary, and confirm that the laboratory holds accreditation for the method.
GRG and composite linings
Glass fibre reinforced gypsum, known as GRG or GFRG, is the usual choice where an interior wants complex three dimensional surfaces in a lining: coffers, curved soffits, fluted panels and decorative ceilings that would be impractical in board. ShapeShell-RG is the ShapeShift GRG system, cast in alpha gypsum as a 3 to 6 mm shell at about 23 kg/m², for interior use only. It is a lining and a decorative element, not an external cladding, and it is not a structural product.
. No fire classification is stated for ShapeShell-RG in this reference, and none should be assumed from the behaviour of gypsum generally: the NCC’s list of materials deemed non-combustible without test covers plasterboard, not every gypsum based product, and in any case the property a lining needs is a group number rather than non-combustibility.
Where a lining specification calls for a classified composite, ShapeShell-RT holds an AS 5637 Group 1 classification from AWTA Product Testing, the best available group number. ShapeShell-RT is a fibre reinforced polymer and is not non-combustible; its Group 1 classification is a lining and reaction to fire classification, not a combustibility one.
Standards and references
- NCC 2022 Volume One Specification 7 Fire hazard properties (check the edition adopted in your jurisdiction)
- AS 5637.1 Determination of fire hazard properties: wall and ceiling linings
- AS ISO 9705 Fire tests: full-scale room test for surface products
- AS/NZS 3837 Method of test for heat and smoke release rates using an oxygen consumption calorimeter
- AS ISO 9239.1 Reaction to fire tests for floorings: critical radiant flux
- AS 1530.3 early fire hazard indices, for materials outside the lining provisions
Related terms
Questions specifiers ask
Do internal wall linings have to be non-combustible?
No. The NCC regulates internal wall and ceiling linings on group number under Specification 7. Non-combustibility applies to external walls of Type A and Type B construction.
What group number does a wall lining need?
It depends on the building class, whether the building is sprinkler protected and where the lining sits. Fire isolated exits are the most demanding, typically Group 1, and general rooms the least.
How is a group number obtained?
By the AS ISO 9705 full room corner test, or by prediction from AS/NZS 3837 cone calorimeter data under AS 5637.1. The room test is the reference method.
Is GRG suitable as a wall lining?
Glass fibre reinforced gypsum is a common interior lining and decorative system, cast in thin shells for complex geometry. Fire classification must be evidenced by test for the specific product.
Are floor finishes covered by group number?
No. Floor coverings are regulated on critical radiant flux to AS ISO 9239.1, a separate test and a separate criterion.
ShapeShell-RG is a cast alpha gypsum system for complex interior linings and decorative elements, from 3 to 6 mm shells at about 23 kg/m². See ShapeShell-RG specifications
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.