Fibre Reinforced Facade Encyclopedia: Testing and standards
The single burning item test is the European intermediate scale reaction to fire test that decides Classes A2, B, C and D under EN 13501-1. Two wings of the product are mounted to form a vertical internal corner, a sand box propane burner is placed at the base of that corner, and the specimen burns for twenty minutes while the heat and smoke it releases are measured in an exhaust hood by oxygen consumption and laser photometry. Its outputs are the fire growth rate index, the total heat released in the first ten minutes, the smoke growth rate index, the total smoke produced, lateral flame spread and the occurrence of flaming droplets.
The corner geometry is the point. A flat specimen radiates heat away; a corner traps it, so flame and hot gas rise faster and a product that looks harmless flat can fail badly in a corner. Real rooms have corners, and most fires start in one.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Standard | EN 13823 Reaction to fire tests for building products: building products excluding floorings exposed to the thermal attack by a single burning item | |
| Specimen | Two wings forming a corner, each 1.5 m high; about 0.495 m and 1.0 m wide | Mounted on the substrate used in service |
| Burner | Sand box propane burner at the base of the corner, about 30.7 kW | Plus a second burner for baseline calibration |
| Duration | 20 minutes | First 600 seconds after ignition used for most indices |
| FIGRA | Fire growth rate index, in W/s | Peak of heat release rate divided by elapsed time |
| THR600s | Total heat release in the first 600 seconds, in MJ | |
| SMOGRA | Smoke growth rate index, in m²/s² | With TSP600s, total smoke production in m², sets the s sub-class |
| Class B limits | FIGRA not more than 120 W/s; THR600s not more than 7.5 MJ; no lateral flame spread to the wing edge | Class C allows 250 W/s and 15 MJ; Class D allows 750 W/s |
| Smoke sub-classes | s1: SMOGRA not more than 30 m²/s² and TSP600s not more than 50 m²; s2: 180 m²/s² and 200 m²; s3: anything else | |
| Droplet sub-classes | d0: none in 600 s; d1: none persisting more than 10 s; d2: anything else |
How the test runs
The two wings are mounted on a trolley to form an L shaped corner meeting at a vertical joint. They are fixed to the substrate and by the method the product will use in service, because both change the result. The trolley is rolled into a frame under a collecting hood connected to an exhaust duct.
A propane sand box burner, calibrated to about 30.7 kilowatts, is positioned at the foot of the corner and lit. A second burner runs away from the specimen for part of the sequence so that the instruments can measure a baseline without the product burning. The test runs for twenty minutes. Throughout, the duct instrumentation measures volume flow, oxygen, carbon dioxide and smoke obscuration, from which the heat release rate and the smoke production rate are computed second by second.
Observers record lateral flame spread, that is whether flame reaches the outer edge of the long wing, and they record flaming droplets or particles falling from the specimen during the first 600 seconds and how long each persists.
What the indices mean
FIGRA is the index that does most of the work. It is computed by dividing the heat release rate at each instant by the time elapsed since ignition and taking the highest value reached, with a threshold applied so that the calculation starts once a defined amount of heat has been released. The effect is to reward slow growth and penalise sharp early peaks, because it is the rate of growth, not the eventual size, that outruns detection and escape.
THR600s is the total energy released in the first ten minutes and measures how much fuel the product actually contributes. A product can have a modest FIGRA and a large THR600s if it burns steadily rather than sharply, and both limits must be met.
SMOGRA and TSP600s are the smoke equivalents, computed the same way from the smoke production rate and the accumulated smoke, and they set the s1, s2 and s3 sub-class. Droplet observations set d0, d1 and d2. The three parts combine into the classification string, so B-s2,d0 means Class B for fire contribution, medium smoke and no flaming droplets.
Where the SBI sits in EN 13501-1
Classes A1 and A2 depend on the furnace test EN ISO 1182 and the calorific value test EN ISO 1716. A2 must then also pass the SBI, at the same FIGRA and THR600s limits as Class B. Classes B, C and D are decided by the SBI together with the small flame ignitability test EN ISO 11925-2. Class E is the small flame test alone, and Class F is the absence of a determined performance.
So the SBI is the pivot of the European system for every product that is not fully inorganic, and it is the test behind the smoke and droplet sub-classes most specifications now call for alongside the letter class.
Why substrate and mounting matter
An SBI classification belongs to a product in a specified end use configuration: a stated thickness, a stated substrate, a stated air gap or absence of one, and a stated fixing method. A thin laminate bonded to a calcium silicate board and the same laminate fixed over a ventilated cavity are different specimens and can fall into different classes, because the cavity changes how heat is retained behind the face and how the specimen distorts.
The classification report states the field of application, and extended application rules can widen it within limits. What a report never supports is the assumption that a thinner version, a different core or a different backing carries the same class. Ask for the classification report rather than a summary certificate.
This is why a European reaction to fire class, on its own, is not accepted as evidence that a facade will perform. The SBI corner is 1.5 metres high with no joints, no brackets and no cavity barriers. Codes that permit combustible cladding at height require a full-scale facade test, BS 8414 with BR 135 in the United Kingdom, AS 5113 in Australia, on the assembly as it will be built.
Where FRP and GRC sit
Cementitious and gypsum products can be tested for Class A1 or A2, and the SBI is only relevant to them on the A2 path. ShapeShell-RC is a glass fibre reinforced concrete system and is Not Deemed Combustible under AS/NZS 1530.1, tested by Ignis Labs.
Fibre reinforced polymer has an organic matrix, cannot pass EN ISO 1182, AS 1530.1 or ASTM E136, and is therefore classified from Class B downward on the strength of its SBI result. Class B with d0 requires a fire retardant resin system and careful laminate design. ShapeShell-RT is classified B-s2,d0 under EN 13501-1 by Intertek Testing Services, holds an AS 5637 Group 1 classification from AWTA Product Testing, and passed the full-scale BS 8414 and AS 5113 test at BRE Global.
Standards and references
- EN 13823 Reaction to fire tests for building products: building products excluding floorings exposed to the thermal attack by a single burning item
- EN 13501-1 Fire classification of construction products and building elements, Part 1
- EN ISO 11925-2 Ignitability of products subjected to direct impingement of flame, single flame source test
- EN ISO 1182 (non-combustibility) and EN ISO 1716 (gross heat of combustion), for Classes A1 and A2
- EN 15725 Extended application reports on the fire performance of construction products and building elements
- BS 8414 with BR 135 and AS 5113, the full-scale facade tests the SBI does not replace
Related terms
Questions specifiers ask
What does the SBI test measure?
Heat release and smoke production from a corner specimen exposed to a 30 kW propane burner for twenty minutes, expressed as FIGRA in W/s, THR600s in MJ, SMOGRA in m²/s² and TSP600s in m², together with lateral flame spread and flaming droplets.
Which EN 13501-1 classes come from the SBI?
Classes A2, B, C and D. A1 comes from EN ISO 1182 and EN ISO 1716 alone; E comes from the small flame test EN ISO 11925-2; F is no determined performance. The s and d sub-classes also come from the SBI.
What are the Class B limits?
FIGRA not exceeding 120 W/s, total heat release in the first 600 seconds not exceeding 7.5 MJ, and no lateral flame spread to the edge of the long wing. Class C allows 250 W/s and 15 MJ; Class D allows 750 W/s.
Why is the specimen a corner?
Because a corner traps radiant heat between two burning faces, which accelerates flame growth. It is a more severe and more realistic geometry than a flat panel, and most room fires begin in or near a corner.
Does an SBI class prove a facade is compliant?
No. The specimen is 1.5 metres high with no joints, cavity or barriers. Codes that allow combustible cladding at height require a full-scale facade test such as BS 8414 with BR 135 or AS 5113 on the assembly as built.
ShapeShell-RT is classified B-s2,d0 under EN 13501-1 by Intertek Testing Services. See the full classification and the tests behind it. See ShapeShell fire test data
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.