ASTM E108 Fire Tests of Roof Coverings

Standard: ASTM E108 – Standard Test Methods for Fire Tests of Roof Coverings

Scope: ASTM E108 is a fire-test-response standard that covers the measurement of the relative fire characteristics of roof coverings to simulate fire sources originating outside the building.

Products: Roof covering materials and roof assemblies

Procedure: ASTM E108 includes five test methods for roof coverings to determine the assembly performance in response to different flame and fire conditions.

Intermittent flame exposure test

The intermittent flame exposure test is required when a roof covering is not restricted for use on noncombustible decks. Steady airflow is applied to the test deck and maintained throughout the test. Flames are applied to the test deck according to the desired Class (see chart ). The airflow remains active until all evidence of flame, glow, and smoke has disappeared from the exposure surface and the material being tested, or until a failure occurs.

Spread of flame test

The spread of flame test is required when a roof covering is not restricted to be used on noncombustible decks. Tests for Classes A and B expose the roof deck to a continuous application of the gas flame and air current for ten minutes or until the flame permanently recedes from the maximum spread point, whichever is shorter. Class C exposes the roof deck to the same conditions for four minutes instead of ten minutes.

Burning brand test

The burning brand test is required when a roof covering is not restricted for use on noncombustible decks. The burning brand test is the most detailed of the ASTM E108 test methods, so we will only cover the basics of this test method.
The brands for Classes A and B are built from dry Doulas fir lumber; Class C brands are built from dry, non-resinous white pine lumber. The brands in all tests must be free of knots and pitch pockets. Brands are conditioned in an oven at 105 to 120°F (41 to 49°C) for a minimum of 24 hours.
Before adding the brands to the roof deck, the brands are ignited by a flame with a temperature of 1630 ± 50°F (888 ± 28°C). Each Class provides detailed, different instructions for how long each face of the brands are held under ignition conditions.
The test ends when the brand is completely consumed and all evidence of flame, glow, and smoke has disappeared from the exposed surface and underside of the roof deck, or until failure occurs.

Flying brand test

The flying brand test is required when there is a possibility that the roof covering will break into pieces of flaming particles that may ignite on the floor. Like the spread of flame test, Classes A and B decks receive a continuous gas flame for ten minutes with Class C decks receiving the flame for four minutes. To determine if flying brands will develop, the air current is maintained at a 12-mph flow until all evidence of flame, glow, and smoke has disappeared from the exposed surface. When treated wood shakes are included in the test sample, the air current is increased to 18 ± 0.75 mph. To achieve a specified Class, the test requires a minimum of two roof decks to pass the performance requirements when tested in sequence

Rain test

A rain test is required whenever the fire performance characteristics of the roof covering material or the roof deck assembly have the potential to be negatively impacted by water. When the rain test is required, six roof decks are prepared and exposed to an environmental cycle. After exposure, the intermittent flame, burning brand, and flying brand tests are conducted each of the tests using two of the six exposed roof decks. The test decks are exposed to twelve one-week cycles, with each cycle consisting of 96 hours of water exposure followed by 72 hours of drying at 140°F (60°C).

Result: The test results will indicate if the roof covering achieves a rating as Class A, B, or C.