UL 790

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These requirements cover the performance of roof covering materials exposed to fire conditions, and are intended to indicate the fire-resistance characteristics of roof coverings when exposed to fire originating from sources outside a building on which the coverings are installed. They are applicable to roof coverings intended for installation on either combustible or noncombustible decks (see 1.7) when the roof coverings are applied as intended.

Class A roof coverings are effective against severe fire test exposures. Under such exposures, roof coverings of this class are not readily flammable, afford a fairly high degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

Class B roof coverings are effective against moderate fire test exposures. Under such exposures, roof coverings of this class are not readily flammable, afford a moderate degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

Class C roof coverings are effective against light fire test exposures. Under such exposures, roof coverings of this class are not readily flammable, afford a measurable degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

Tests conducted in accordance with these requirements are intended to demonstrate the performance of roof coverings during the types and periods of exposure involved, but are not intended to determine the acceptability of roof coverings for use after exposure to fire.

Roof covering materials are required to comply also with the requirements for construction, material specifications, and performance as applicable to specific types, designs, sizes, and arrangements. All such applicable additional requirements are not considered to be within the scope of these requirements for fire tests, but are included in the applicable standards covering the material in question.

A combustible deck is formed of wood (sheathing boards or plywood). A noncombustible deck is formed of metal, concrete, or poured gypsum.