Class C roof assemblies are those that can withstand a mild fire test. Class C roof assemblies and roof coverings must be listed and identified by an accredited testing agency. Most class C roofing materials will pass this test with no changes to the roof itself or its covering.
The American National Standards Institute (ANSI) developed standards for classifying building materials by fire resistance. These classes indicate how well a material will resist burning when exposed to the heat of a flame. The classification system ranges from class A, which represents the most resistant material, to class F, which represents the least resistant material.
Building materials are given one of these four classifications based on their ability to resist burning:
Class A - Will not burn under normal conditions. Examples include steel and concrete.
Class B - Will burn but not affect the environment. Examples include wood and some plastics.
Class C - May burn but may also cause smoke damage. Examples include asphalt shingles, fiberglass insulation, and clay tiles.
Class D - Will burn and release toxic gases. Examples include leather, paper, and cloth.
Class E - Explodes on contact with air.
This standard includes three types of fire exposure: * Class A roof coverings, which are effective against severe fire test exposures; * Class B roof coverings, which are effective against moderate fire test exposures; and * Class C roof coverings, which are effective against severe fire test exposures. *Class C roof coverings, which are resistant to mild fire test exposures. They offer protection from smoke, water, and heat damage for up to 20 years. The material used in class C roofs provides more protection than class B materials but not as much as class A materials.
*Class A roof coverings, which are effective against severe fire test exposures. They offer protection from smoke, water, and heat damage for up to 50 years. The material used in class A roofs provides greater protection than class B materials but not as great as class AA or AAA materials.
*Class BB roof coverings, which are effective against moderate fire test exposures. The material used in class BB roofs provides greater protection than class B materials but not as great as class AA or AAA materials.
*Class CC roof coverings, which are effective against slight fire test exposures. They offer protection from smoke, water, and heat damage for up to 10 years.
A Class 1 roof has been subjected to a battery of tests that examine the complete roof assembly, including the exterior spread of flame test used for the Class A classification. Although all Class 1 roof assemblies are Class A roofs, not all Class A roof systems are Class 1 rated. A Class 1 roof requires a special testing procedure conducted by an independent testing agency such as Underwriters Laboratories (UL).
Class 1 roofs are required by law in some states for new buildings. They provide an absolute maximum safety requirement for the building and its contents should any fire damage occur. Class 1 roofs are also required by law for certain types of existing buildings. If a building lacks a proper Class 1 roof it can be classified as a Class 3 or lesser roof system which is less safe than a Class 1 roof.
Class 1 roofs are made up of several components: metal decking supported by steel posts driven into the ground or concrete slabs; insulation between the decking and the top of the building structure known as the cap sheet; and a protective covering over the entire roof consisting of multiple layers of material intended to prevent sparks from burning through.
The type of material used in the construction of the roof affects how easily it will burn. Metal decks and steel support beams on Class 1 roofs conduct heat rapidly, while wood shingles and tiles used on lesser-rated roofs retain their warmth for longer periods of time.