Class A, B, or C represents fire ratings for roofing materials but some materials are simply unrated if a roof covering cannot meet the requirements to be included in any class.
The highest rating is Class A, which means that it includes the materials creating the most fire resistant roofs: metal roofs, concrete tiles, clay tiles, slate roofing and fiberglass asphalt composition shingles. These materials require no special treatments to be rated Class A. However, some of them are very heavy (slate, clay, concrete) and in some severe cases, if the fire progresses too much, fire fighters may not be allowed to intervene, because if such a heavy roof collapses on them it can produce another disaster.
Other materials are rated Class A only if additional materials are used to increase protection and attain the fire rating: aluminum, rubber or recycled plastic products.
On the other hand, traditional wood shakes that are not treated with any fire retardant are an example of unrated material. Wood shakes that are impregnated with such a solution can meet the requirements for being rated Class B.
Class A fire rated roofing materials are a great choice especially if the building is located in a wildfire-prone area.
Talk to fire resistant commercial roofing Colorado Springs CO companies for the latest information on fire resistant roofing. They will be the best resource in understanding your options.