23 May Safely covered?
Esther Gitau, Testing Technician, Emirates Safety Laboratory (ESL) explains ASTM E108 – a standard test method for evaluating the fire performance of roof coverings which determines the fire characteristics of various roof coverings, including asphalt shingles, tiles, slates, metals, and wood.
This test method evaluates the performance of roofing materials subjected to simulated fire conditions emanating from outside the building. A gas burner and burning brands are used as fire sources. The test provides information about the ability of roofing material to resist ignition, prevent the spread of fire, and maintain its structural integrity during a fire. The tests also evaluate whether the roof coverings will produce flying materials (flying brands) when exposed to simulated winds of 12 mph during the fire tests.
The test method applies to roof coverings intended to be installed over combustible (plywood, wood, OSB) or non-combustible decks (gypsum, metal).
The ASTM E108 test standard comprises six methods:
- Intermittent flame exposure test
- Spread of flame test
- Burning brand test
- Flying brand test
- Rain test
- Weathering test
Intermittent flame exposure test
The test is performed on at least two 4ft-4 in. long by 3ft-4 in. wide test decks. The decks are mounted at an incline specified by the manufacturer. A gas flame from the burner is applied intermittently at specified intervals depending on the intended class rating of the roof covering. The calibrated air supply is maintained throughout the test until all sign of flaming, glowing or smoking over the roof covering and below the test deck has disappeared or until failure arises.
Spread of flame test
A minimum of two decks are tested for the spread of flame. The deck length depends on the desired class rating: At least 8 ft for Class A tests, a minimum of 9 ft for Class B tests and 13 ft for Class C tests. The gas flame and air current are applied for 10 min for Class A and B tests and 4 min for Class C tests.
Burning brand test
4 ft-4 in. long test decks are mounted at the desired incline, and the calibrated air supply is applied. Four decks are tested for Class A ratings, and two decks for Class B and C ratings. In this test, the gas burner is detached to prevent airflow obstruction to the roof coverings. Class A brands are 12 in. square and 21/4 in. thick, Class B brands are 6 in. square and 21/4 in. thick, and Class C brands are 11/2 in. square and 25/32 in. thick. The brands are ignited for the specified times before their application on the test decks by subjecting them to a gas burner flame of defined flame temperature that envelops them entirely. The tests are run until the brands are fully consumed and when all indication of smoking, flaming and glowing on the roof covering and below the test deck has wholly disappeared.
Flying brand test
A minimum of two decks, 4ft-4 in. long, are tested. The gas flame is applied continuously for 10 min for Class A and B tests and 4 min for Class C tests. A 12-mph air current is maintained until flaming, glowing, and smoking has disappeared from the surface of the roof covering.
The test is conducted on six decks, 4ft-4 in. long, mounted at an incline of 4 in. per horizontal foot. Spray nozzles are mounted 7 ft above the test decks. The test decks are subjected to 12 1-week cycles, with one cycle comprising 96 hours of water exposure and 72 hours of drying time at 140° F.
The test decks are mounted outdoors and are tested following exposures of 1, 2, 3, 5 and 10 years.
Only the spread of flame test is to be conducted for roof coverings that are expected to be installed solely on non-combustible decks. The test method allows the roof covering materials to be tested when applied on combustible or non-combustible decks of the specified lengths.
When the roof covering is not limited to use on non-combustible tests, the intermittent flame test, spread of flame test and the burning brand test are required.
Flying brand tests are required where there is a likelihood that the roof covering material will break into flaming particles that would support combustion on the floor.
The rain and weathering tests apply to roof covering materials whose fire-retardant properties are expected to be adversely affected by rain or weathering outdoors.
Evaluation of test results
After the tests are completed, the results are evaluated to determine the fire performance of the roof covering material.
The fire performance is based on several factors, including the flame spread, the appearance of flaming on the underside of the test deck, the production of flaming and glowing brands, the dislodgment of portions of the test sample and the ability of the material to maintain its structural integrity during the test.
The flame spread distance is a measure of the distance to which the flaming of the roof covering material has reached. A lower flame spread distance indicates that the material will contribute less to the development of a fire.
The ability of the material to maintain its structural integrity during the test is also evaluated. If the roofing material can retain its structural integrity during the test, it is considered to be better able to resist fire.
The test results indicate whether the roof covering material attains either of the three classifications: Class A, Class B or Class C.
The ASTM E108 test method is suitable for evaluating roof coverings’ fire performance properties.
Certification bodies, like Emirates Safety Laboratory (ESL), use this method and the results of testing to this standard when making a certification decision and issuing a certificate of conformity.
The Certificate of Conformities (CoCs) based on the ASTM E108 test method assists manufacturers, project owners, designers, consultants, fabricators, and contractors in making informed decisions about fire safety on project roofing materials.