Roofing Material Fire Ratings

Understanding roof fire ratings class a roofing.

Roofing material fire ratings.

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. An exterior fire retardant treated shake roof has a stand alone class b rating. 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. Class c fire resistant roofing material.

Obviously since wildfires and the fire season has become increasingly worse it is important to note the roofing materials that are the lowest rated. But by including a particular underlying material it can meet the requirements for a class a roof. 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. Wood shake plywood or particle board roof are the most common roofing types listed as class c.

The maximum flame spread is 6 feet for a class a rated roof 8 feet for class b and 13 feet for class c. This month let s take a closer look at one particular type fire ratings. 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. 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.