Roof Assembly Fire Class

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

Roof assembly fire class.

Class a roof assemblies shall be permitted for use in buildings or structures of all types of construction. Assembly rated class a roof coverings are those that meet class a standards when combined with other elements. 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.

In accordance with these standards all classified roof covering assemblies fall into one of the three following categories. The best rating achieved is class a which is described by ul as effective against severe fire exposure class 1 rating. 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. Examples of a by assembly fire rating include fire retardant treated wooden shakes and aluminum roof coverings.

An exterior fire retardant treated shake roof has a stand alone class b rating. Class a roof assemblies and roof coverings shall be listed and identified as class a by an approved testing agency. But by including a particular underlying material it can meet the requirements for a class a roof. The maximum flame spread is 6 feet for a class a rated roof 8 feet for class b and 13 feet for class c.