Roof Assembly Fire Class

Examples of a by assembly fire rating include fire retardant treated wooden shakes and aluminum roof coverings.

Roof assembly fire class.

In accordance with these standards all classified roof covering assemblies fall into one of the three following categories. Class a roof assemblies shall be permitted for use in buildings or structures of all types of construction. An exterior fire retardant treated shake roof has a stand alone class b rating. Class a roof assemblies are those that are effective against severe fire test exposure.

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. 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 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. Includes roof coverings which are effective against moderate fire exposures.

But by including a particular underlying material it can meet the requirements for a class a roof. Includes roof coverings which are effective against severe fire exposures class b. The best rating achieved is class a which is described by ul as effective against severe fire exposure class 1 rating. The maximum flame spread is 6 feet for a class a rated roof 8 feet for class b and 13 feet for class c.