Roof Assembly Fire Class

Includes roof coverings which are effective against severe fire exposures class b.

Roof assembly fire class.

Class a roof assemblies and roof coverings shall be listed and identified as class a by an approved testing agency. Examples of a by assembly fire rating include fire retardant treated wooden shakes and aluminum roof coverings. 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. Assembly rated class a roof coverings are those that meet class a standards when combined with other elements.

An exterior fire retardant treated shake roof has a stand alone class b rating. In accordance with these standards all classified roof covering assemblies fall into one of the three following categories. The class 1 rating is an exclusive designation that can only be awarded by fm global which indicates the successful testing of the entire roof assembly using fm approval standard 4470. But by including a particular underlying material it can meet the requirements for a class a roof.

Class a roof assemblies are those that are effective against severe fire test exposure. The slope of the test specimen is preselected and since steeper slopes are more of a challenge due to melting material feeding the fire the rating applies to the maximum slope passed. According to the scope of fm 4470. Includes roof coverings which are effective against moderate fire exposures.