Fibre Reinforced Facade Encyclopedia: Testing and standards
ASTM E84 is the United States standard test method for the surface burning characteristics of building materials. A specimen is mounted face down in the ceiling of a 7.6 metre (25 ft) horizontal tunnel, a gas burner is lit at one end under a controlled draught, and for ten minutes observers record how far flame travels while a photometer in the exhaust duct measures smoke. The results are two dimensionless numbers: a Flame Spread Index (FSI) and a Smoke Developed Index (SDI). Class A, the best grade, is FSI 0 to 25 with SDI not exceeding 450.
The indices are comparative, not absolute. The scale is fixed by two reference materials burned in the same tunnel: inorganic reinforced cement board is 0 and select grade red oak flooring is 100. An FSI of 25 means flame travelled about a quarter as far, as fast, as it does over red oak.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Standard | ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Materials | |
| Identical methods | UL 723, NFPA 255, CAN/ULC S102 | Same tunnel, same indices |
| Tunnel | 7.6 m (25 ft) long, about 450 mm (17.75 in) wide | Specimen forms the ceiling |
| Specimen | About 7.3 m (24 ft) by 510 mm (20 in) | Tested in the mounting used in service |
| Fire source | Twin gas burners at about 89 kW (5,000 Btu/min) | Draught about 1.2 m/s (240 ft/min) |
| Duration | 10 minutes | |
| Class A (Class I) | FSI 0 to 25, SDI 0 to 450 | Required for exits and many exterior uses |
| Class B (Class II) | FSI 26 to 75, SDI 0 to 450 | |
| Class C (Class III) | FSI 76 to 200, SDI 0 to 450 | |
| Referenced by | IBC Chapter 8 for interior finish; Chapters 14 and 26 for exterior materials | Edition adopted locally governs |
How the tunnel test runs
The Steiner tunnel is a long, narrow, refractory lined box with a removable ceiling. The specimen is fixed in place as the ceiling, face down over the full length. Air is drawn through at a set velocity, the burners at the inlet end are ignited, and the flame front is read through viewing ports along the side wall. Flame spread distance against time is integrated into the Flame Spread Index. At the same time light transmission through the exhaust is recorded and integrated into the Smoke Developed Index.
Both indices are calculated relative to the calibration burns, so neither is a physical quantity with units. That is why a Flame Spread Index of 20 cannot be converted into a heat release rate, a European class or an Australian group number. It can only be compared with other Flame Spread Indices measured in the same way.
What the International Building Code requires
For interior wall and ceiling finishes, IBC Chapter 8 sets the required class by occupancy group and by location in the building, with Class A generally required in exits and vertical exit enclosures, Class A or B in corridors, and Class C acceptable in many rooms and enclosed spaces. Sprinkler protection relaxes some of the requirements by one class.
On the outside of a building the test has a narrower role. Exterior materials are covered in Chapter 14 and, for specific material families, in Chapter 26. Fibre reinforced polymer used as exterior cladding on Type I to IV construction must meet Class A under ASTM E84 and, above the height threshold in the code, must also be part of an assembly that has passed NFPA 285. The flame spread class qualifies the material; the full-scale test qualifies the wall.
What the test does not tell you
- It is a surface test on a specimen in the ceiling orientation, so materials that soften, melt or fall away can produce a low index that does not reflect their behaviour in a vertical wall
- It measures nothing about the assembly: no cavity, no insulation, no fixings, no joints
- It says nothing about combustibility; a Class A result does not make a material non-combustible, which is settled by ASTM E136
- It says nothing about fire resistance, which is measured on assemblies under ASTM E119
- It does not translate into EN 13501-1 classes or AS 5637.1 group numbers
How ASTM E84 compares with the Australian and European tests
Australia uses AS 1530.3 to measure ignitability, spread of flame, heat evolved and smoke developed as four separate indices, and AS 5637.1 to convert cone calorimeter or room test data into a group number from 1 to 4. Europe uses the single burning item test in a corner configuration to produce an EN 13501-1 class from A1 to F with smoke and droplet sub-classes. All three regimes answer the same broad question about how a product reacts to fire, and none of them is a translation of another. A product sold in Australia, Europe and North America needs the test each code names.
The practical consequence for specification is that a fire test package for an internationally supplied facade product is a set of reports, not one certificate. The Global Facade Fire Standards Atlas on this site sets the regimes out side by side.
Composite cladding materials in the tunnel
Glass fibre reinforced concrete, fibre cement, terracotta and stone are inorganic and typically return indices at or close to zero, although they rarely need the test because they can pass the combustibility test instead. Fibre reinforced polymer is combustible and does need a flame spread class: a Class A result is achievable with a fire retardant resin system, mineral fillers and a controlled laminate, and it is the entry condition for FRP cladding under the IBC.
ShapeShift publishes ShapeShell-RT results against AS 5637 (Group 1, AWTA Product Testing), EN 13501-1 (B-s2, Intertek) and the full-scale BS 8414 and AS 5113 test at BRE Global.
Standards and references
- ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Materials
- UL 723, NFPA 255 and CAN/ULC S102 (equivalent tunnel methods)
- International Building Code Chapter 8 (interior finishes), Chapter 14 (exterior walls), Chapter 26 (plastics and fiber reinforced polymer)
- ASTM E136 (combustibility) and ASTM E119 (fire resistance of assemblies)
- NFPA 285 (exterior wall assemblies containing combustible components)
- AS 1530.3 and AS 5637.1 (Australia); EN 13501-1 (Europe and UK)
Related terms
Questions specifiers ask
What is a Class A flame spread rating?
A result under ASTM E84 with a Flame Spread Index of 0 to 25 and a Smoke Developed Index of no more than 450. It is also written as Class I. Class B is FSI 26 to 75 and Class C is FSI 76 to 200.
Does Class A mean non-combustible?
No. Non-combustibility in the United States is decided by ASTM E136, a furnace test. Many Class A materials are combustible products with fire retardant treatment. The two results answer different questions.
Is ASTM E84 the same as ASTM E119?
No. ASTM E84 measures how flame spreads across the surface of a material in ten minutes. ASTM E119 measures how long a complete wall, floor or roof assembly resists a standard furnace fire, in hours. One is reaction to fire, the other is fire resistance.
Can an ASTM E84 result be used for NCC compliance in Australia?
Not directly. The NCC references AS 1530.1, AS 1530.3, AS 5637.1 and AS 5113. A tunnel test result is supporting information for a fire engineer, not a substitute for the Australian tests.
Does FRP cladding need ASTM E84 in the United States?
Yes. Fibre reinforced polymer used on the exterior of Type I to IV construction must achieve Class A under ASTM E84, and above the height threshold in the code the assembly must also pass NFPA 285.
Specifying a composite facade across several markets? ShapeShift publishes each fire result against the standard and the testing body that issued it. Open the fire standards atlas
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.