Class C fire resistance is a rating given to building materials, including roofing materials, that have been tested and found to have a low level of fire resistance. The Class C rating is based on a standardized testing system, such as the ASTM E108 or UL 790 test, and indicates that the material has the ability to withstand only minor fire exposure without contributing to the spread of flames or the intensity of the fire.

In roofing, materials with a Class C fire resistance rating are typically made from less fire-resistant materials, such as organic asphalt shingles, that are not treated with fire retardant chemicals. While these materials are designed to provide a certain level of protection against fire, they may not be able to withstand more severe fire exposure, and can contribute to the spread of flames and the intensity of the fire.

Building codes and regulations often require that roofing materials meet certain fire resistance ratings, and many insurance companies offer discounts or other incentives for buildings that are equipped with higher-rated, fire-resistant roofing materials.

Overall, Class C fire resistance is the lowest level of fire resistance rating for roofing materials, and may not provide adequate protection in the event of a fire. Building owners and occupants should consider the risks and benefits of using Class C fire-resistant roofing materials, and may want to consider upgrading to materials with a higher rating for increased protection and peace of mind.