While there are many types of fire ratings issued by U.L., there are few online resources that that provide specific information about the Class A Fire Rating, Class B Fire Rating, Class C Fire Rating and Class D Fire Rating.
For the most part, these ratings are placed upon roofing materials. But there are additional fire ratings for Fireproof Doors.
Doors are constructed to conform within requirements specified by Underwriter's Laboratories, Inc. (U.L.) Doors are automatic and self-closing, Class (A) (8) (C) (D) or oversized certificate.
CLASS (A) -3 hour approved for doors in dividing fire walls with openings not exceeding 1,200 sq. ft. in area.
CLASS (B) -1.5 hour approved for doors, in vertical shall openings not exceeding 1,200 sq. ft. in area.
CLASS (C) -0.75 hour approved for doors in corridor or room-partition opening not exceeding 1,200 sq. ft. in area.
CLASS (D) -1 .5 hour approved for doors in exterior wall opening not exceeding 1,200 sq. ft. in area.
Roofing Material Fire Ratings
Class A-rated roof assemblies are effective against severe fire test exposure. A Class A fire rating is the most stringent rating available for exterior fire resistance. Class B-rated roof assemblies are effective against moderate fire test exposure. And Class C-rated roof assemblies are effective against light fire test exposure. A Class C fire rating is the least stringent rating available for exterior fire resistance. If a roof assembly cannot pass the Class C criteria, it typically is considered to be non-classified.
It is important to realize Class A-rated roof assemblies are required for few buildings. According to IBC, a Class A-rated roof assembly only may be necessary if it is part of interior fire-rating requirements, a building is located in a specific fire district, or the Urban-Wildland Interface Code also applies and specifically requires a Class A-rated construction.
Detailed information regarding specific roof exterior and interior fire-resistance ratings are provided in FM's Approval Guide and UL's Building Materials Directory and Fire Resistance-rated Construction Directory . UL's directory information also is available online at www.ul.com .