Roof covering

A covering is the visible outer layer: shingles, tile, metal panels or membrane on a roof; siding or cladding on a wall. Class A, B and C are not properties of a covering by itself. ASTM E108 and UL 790 are fire tests of roof coverings applied as intended on a deck, with the underlayment the test used, and the class describes that covering-on-the-tested-deck under intermittent flame, spread of flame and a burning brand. Change the deck or leave out the named underlayment and the class does not follow. That is why "Class A shingles" is on this site's do-not-say list and covering versus assembly exists.

Class A, B and C. A is the most severe exposure and the highest protection to the deck; C the least. California's CWUIC 504.2 requires Class A in mapped areas, with named exceptions treating some masonry, metal, tile and slate assemblies as Class A without the test. Oregon R327, where adopted, names asphalt, slate, metal, or clay, concrete and tile roofing, or an equivalent to a minimum Class B assembly, and bans wood shingles and shakes; profile gaps between covering and deck must be closed, fireblocked or covered with a 72-pound cap sheet. Kittitas County wants no less than Class A in high and extreme hazard areas and Class C in low and general ones.

The deck beneath. OSFM handbook category 8180 lists non-wood roof coverings by ID with the deck and underlayment tested; how to read a Class A roof listing shows that a sibling row and an underlayment listing are not the same roof. IBHS Wildfire Prepared writes Class A roof covering and still means the tested system. Walls have the same shape: siding is a covering, and Oregon R327's wall paths are a noncombustible or ignition-resistant covering, or an ASTM E2707-tested assembly. The roofing hub holds the listed systems.