Roofing Material Fire Ratings

Obviously since wildfires and the fire season has become increasingly worse it is important to note the roofing materials that are the lowest rated.

Roofing material fire ratings.

An exterior fire retardant treated shake roof has a stand alone class b rating. Class c fire resistant roofing material. In a recent roofing column we focused upon technical information that could be found on roofing material wrappers that could verify compliance with various building codes. But by including a particular underlying material it can meet the requirements for a class a roof.

Wood shake plywood or particle board roof are the most common roofing types listed as class c. Fires that originate outside of the structure itself. Class a roofing is the preferred choice for any home but this type of roofing is particularly important if you live in an area that is prone to wildfires to achieve a class a rating the roof must be effective against severe fire exposure. Astm ul 790 tests for fire resistance of roof covering materials underwriters laboratories has defined the ul 790 standard tests of roofing material fire resistance to external fire sources.

Common underlying materials include a type 72 roll roofing material also known as 72 pound felt or 72 pound capsheet material and a panelized gypsum product called densdeck. The maximum flame spread is 6 feet for a class a rated roof 8 feet for class b and 13 feet for class c. 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. Ul 790 underwriters laboratories roof fire ratings a b c tests.