Flame Spread Index For Class A Roof

The nature of the surfacing and the slope of the roof greatly affect spread of flame.

Flame spread index for class a roof. 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. An fm class 1 designation means the roof assembly has been subjected to a series of tests in addition to external and internal fire exposure including wind uplift water leakage and impact resistance. Flame spread 25 or less frtw some fr surface coatings class b or ii. Flame spread and smoke development astm e84 in order to obtain the flame spread classification results must fall into a range between 0 and 25 to be class a 26 75 for class b and 76 200 for class c.

The flame spread categories are as follows per astm e 84 ul 723. And class iii or c with a 76 200 fsr. On very low slope commercial structures even a glaze coating of pure asphalt may meet class a flame spread. Class i or a with a 0 25 fsr.

Flame spread 76 to 200 untreated lumber and plywood. 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 scale is divided into three classes. Gravel surfaced built up roofing and ballasted single ply systems usually meet class a while mineral surfaced roofings may be class b.

The most commonly used flame spread classifications are. Class a products will not generate excessive visibility obscuring smoke an important factor in designing safe egress for building occupants. Smoke developed index 0 450 fire class a designation refers to material that may ignite but will not sustain a flame. Fsi is the measurement for the speed at which flames progress across the interior surface of a building while sdi measures the amount of smoke a sample emits as it burns.

Through the e 84 test both the flame spread index fsi and smoke developed index sdi are reported for a given sample. This is proven if it can. Polyiso remains the only foam plastic insulation product for direct application to steel roof decks to earn fm approval for class 1 roof systems. In all cases smoke development must be less than 450.

Flame spread 26 to 75 other fr surface coatings class c or iii. Class a or i. Foam plastic used for insulating interior walls ceilings and floors of commercial buildings requires class i foam having a flame spread index of 75 or less in some circumstances 25 or less and smoke developed index of 450 or less. Lexan thermoclear thermoclick and corrugated sheet products have a class a.

Class ii or b with a 26 75 fsr. In general inorganic materials such as brick or tile are class i materials. When conducting healthcare renovations almost all facilities require temporary containment materials to be used the meet the astm e 84 class a fire rated requirement. Experience maximum flame spread of 6 feet.

To achieve a class a rating the roof must be effective against severe fire exposure. Fibrated coatings and asphalt emulsions retain the class a to higher slopes as do the fr modified and fr single ply systems.