SpecTopics: Class A, B, and C - UL Fire Classifications for Roofs
UL tests the fire resistance of roof construction using External Fire Ratings (Class A, B, or C searched for on the UL website using the UL Category Code TGFU) and Internal Fire Ratings (hourly constructions – P numbers searched for on the UL website using the UL Category BXUV). This SpecTopic is going to focus on the External Fire Ratings.
As outlined in the International Building Code (IBC), all roof coverings are required to be tested in accordance with ASTM E108 or UL 790. The minimum roof coverings installed on buildings shall comply with Table 1505.1 based on the type of construction of the building. This table is recreated from the 2015 IBC below. There are a few footnotes on some types of occupancy classifications and project types, so please consult the actual Table 1505.1 in the edition of IBC adopted by your local building official.
TABLE 1505.1 Minimum Roof Covering Classification for Types of Construction
As seen in the table, Class A roofing is not a minimum requirement when used in any type of construction; however, many architects today specify Class A roof systems as way of making sure they meet the minimum code requirements for every project. This practice is certainly acceptable but can be confusing to some architects when asked about the 3 classes.
Class A fire testing is considered severe fire test exposure, while Class B is considered moderate fire test exposure and Class C is considered light fire test exposure. Under all of these tests, roof coverings afford a level of fire protection (severe for A, moderate for B, and light for C) to the roof deck, do not slip from position, and are not expected to produce flying brands. These tests are conducted on either combustible or non-combustible roof decks.
The Standard Test Methods for Fire Tests of Roof Coverings, UL 790 (ASTM E108), includes three key tests to provide fire classification of roof covering materials and systems. These are the Spread of Flame Test, Intermittent Flame Test, and Burning Brand Test. During the Burning Brand Test, heat is transferred directly through the roof covering (single-ply, BUR, shingles, etc.) and the other roof components (insulation, underlayments, etc.) protecting the roof deck. In most Burning Brand Tests conducted over a combustible deck (3/8- or 15/32- inch plywood), the roof components play a significant role in achieving the fire rating of the overall roofing system. Accordingly, many certifications of roof covering materials describe the specific types of roof components to be used based on the testing conducted.
For more information on which Carlisle membranes meet Class A, B, and C and in what configurations of roofing components, check out our Code Approval Guides for each membrane type (EPDM, TPO, PVC, and KEE HP) by visiting the Carlisle SynTec website or clicking here.
As outlined in the International Building Code (IBC), all roof coverings are required to be tested in accordance with ASTM E108 or UL 790. The minimum roof coverings installed on buildings shall comply with Table 1505.1 based on the type of construction of the building. This table is recreated from the 2015 IBC below. There are a few footnotes on some types of occupancy classifications and project types, so please consult the actual Table 1505.1 in the edition of IBC adopted by your local building official.
TABLE 1505.1 Minimum Roof Covering Classification for Types of Construction
| IA | IB | IIA | IIB | IIIA | IIIB | IV | VA | VB |
| B | B | B | C | B | C | B | B | C |
As seen in the table, Class A roofing is not a minimum requirement when used in any type of construction; however, many architects today specify Class A roof systems as way of making sure they meet the minimum code requirements for every project. This practice is certainly acceptable but can be confusing to some architects when asked about the 3 classes.
Class A fire testing is considered severe fire test exposure, while Class B is considered moderate fire test exposure and Class C is considered light fire test exposure. Under all of these tests, roof coverings afford a level of fire protection (severe for A, moderate for B, and light for C) to the roof deck, do not slip from position, and are not expected to produce flying brands. These tests are conducted on either combustible or non-combustible roof decks.
The Standard Test Methods for Fire Tests of Roof Coverings, UL 790 (ASTM E108), includes three key tests to provide fire classification of roof covering materials and systems. These are the Spread of Flame Test, Intermittent Flame Test, and Burning Brand Test. During the Burning Brand Test, heat is transferred directly through the roof covering (single-ply, BUR, shingles, etc.) and the other roof components (insulation, underlayments, etc.) protecting the roof deck. In most Burning Brand Tests conducted over a combustible deck (3/8- or 15/32- inch plywood), the roof components play a significant role in achieving the fire rating of the overall roofing system. Accordingly, many certifications of roof covering materials describe the specific types of roof components to be used based on the testing conducted.
For more information on which Carlisle membranes meet Class A, B, and C and in what configurations of roofing components, check out our Code Approval Guides for each membrane type (EPDM, TPO, PVC, and KEE HP) by visiting the Carlisle SynTec website or clicking here.
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