Roof covering classifications are based on their ability to resist fire spread from external sources. Class C roof coverings are tested and proven to be effective against light fire exposures. They are designed to not slip from position, produce flying brands, or allow the fire to penetrate the roof deck under these light exposure conditions. This classification represents the minimum level of fire resistance for rated roof coverings, affording a slight degree of fire protection. The classifications descend from Class A (severe exposure) to Class B (moderate exposure) and finally to Class C (light exposure).

A. Class A coverings: These are effective against severe fire exposures, offering the highest degree of fire protection, not light exposures.

B. Class B coverings: These are effective against moderate fire exposures, which is a higher level of protection than required for light exposures.

D. Class D coverings: This is not a standard classification for fire-retardant roof coverings in the NFPA or International Building Code systems.

1. National Fire Protection Association (NFPA). (2023). Fire Protection Handbook (21st ed.). Section 16, Chapter 4, "Roof Coverings and Roof Deck Assemblies," pp. 16-68 to 16-69.

2. International Code Council (ICC). (2021). International Building Code (IBC). Chapter 15, Section 1505.4, "Class C Roof Assemblies."

3. Oklahoma State University, College of Engineering, Architecture and Technology. (n.d.). FST 2133: Building Construction for Fire Protection, Chapter 4: Building Materials and Structural Systems. Courseware materials describe roof covering classifications, defining Class C as providing protection against light fire hazards.