Roof Assembly Fire Class

In accordance with these standards all classified roof covering assemblies fall into one of the three following categories.

Roof assembly fire class.

An exterior fire retardant treated shake roof has a stand alone class b rating. Includes roof coverings which are effective against severe fire exposures class b. According to the scope of fm 4470. 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.

But by including a particular underlying material it can meet the requirements for a class a roof. 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. 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. Class a roof assemblies and roof coverings shall be listed and identified as class a by an approved testing agency.

Class a roof assemblies are those that are effective against severe fire test exposure. Assembly rated class a roof coverings are those that meet class a standards when combined with other elements. Examples of a by assembly fire rating include fire retardant treated wooden shakes and aluminum roof coverings. Class a roof assemblies shall be permitted for use in buildings or structures of all types of construction.