Roof Assembly Fire Class Criteria

Class a does not mean grade a roofing systems are rated by realistic fire tests.

Roof assembly fire class criteria.

Class a roof assemblies shall be permitted for use in buildings or structures of all types of construction. Class a roof assemblies and roof coverings shall be listed and identified as class a by an approved testing agency. Roofing systems must meet or exceed building codes and insurance requirements. Fire ratings may pertain to resistance to fire from above the roof system the familiar class a b or c ratings or fire exposure from the building interior the underside of the roof deck.

But by including a particular underlying material it can meet the requirements for a class a roof. 1505 2 class a roof assemblies class a roof assemblies are those that are effective against severe fire test exposure. Test conditions and pass criteria are shown in table 1. B or c roof assembly a class a b or c assembly cannot be.

Tested roof systems are fire classified class a b or c where the most fire resistant roof assemblies are class a and class c is least resistant. We must emphasize however that individual roof components are not rated at all. A roofing membrane that is classified as part of a class a assembly when installed over a particular insulation may not qualify as part. For example shake roofing with a fire retardant treatment rates class b on its own but achieves a class a rating when combined with specified underlying materials such as type 72 roll roofing material.

Class a roof assemblies are those that are effective against severe fire test exposure. Class a roof assemblies shall be permitted for use in buildings or structures of all types of construction. 1 an intermittent flame test in which the flame is turned on and off during the roof assembly to resist. Examples of a by assembly fire rating include fire retardant treated wooden shakes and aluminum roof coverings.

Building code fire resistance requirements building codes establish fire resistance requirements for roofs based on the type of construction e g concrete steel wood for the building. It should be noted that these classifications apply to roofing assemblies and not the roofing membrane. Class a roof assemblies and roof coverings shall be listed and identified as class a by an approved testing agency. 6 usg fire resistant assemblies test certification test conditions and fire and sound tested assemblies listed in this selector are based on characteristics properties and performance certificationof materials and systems obtained under controlled test conditions as set forth in the appropriate astm standard in effect at the time of test.

For roof assemblies with combustible decks wood plank t g astm e 108 and ul 790 require two additional fire tests. Roofing assembly classification will need to be for each roofing project. Assembly rated class a roof coverings are those that meet class a standards when combined with other elements.