How Long Does A Roof Have To Be Fire Resistant

Fire resistance ratings are expressed in the number of minutes or hours a structure can withstand a fire simulation test.

How long does a roof have to be fire resistant.

Structural fire resistance periods vary between 30 60 and 90 minutes according to the occupancy and the height of the building and requirements change at 5 18 and 30 metres. Wood shake plywood or particle board roof are the most common roofing types listed as class c. Because asphalt shingles are relatively inexpensive they are the most common roofing material especially in areas where fire isn t an ever present danger. Class b fire retardant treatment is effective against moderate fire exposures.

To meet class a the test specimen must resist 15 cycles class b eight cycles and class c three cycles. Fire burning through to the underside of this roof covering assembly into what would be the attic indicates that as constructed this roof covering does not qualify for a class a fire rating. In north america fire safety codes have dictated for decades that building materials used on the exterior of the home including roofing materials should have a certain level of fire resistance. A gas flame is cycled on and off.

For example an office that is less than 18m tall must maintain structural stability for 60 minutes during a fire. Some building jurisdictions now require a fire watch for a minimum of one hour after the last roofing torch has been extinguished. Fire resistance ratings time temperature include structural elements and everything above including the roof membrane and its surfacing. During construction there are many opportunities for accidental ignition including welding of steel and the use of torches on modified bituminous roof membranes.

The white colored material is a panelized gypsum fiberglass product that can be used to attain a by assembly class a fire rating. As many people know wood is fuel for a fire despite the fact that it is a valuable and reliable roofing material. Note that underwriters laboratories has had a fire resistance test for roof coverings including shingles since 1958. Don t be left hanging understanding how the nec regards suspended ceiling designs and supports is critical for proper design and installation of electrical wiring and equipment.

As a designer and installer you should know the fundamental differences between a suspended ceiling which is an integral part of a fire rated floor ceiling or roof ceiling assembly and the far more. The intermittent flame test. Under such exposures roof coverings of this class are not readily flammable afford a moderate degree of fire protection to the roof deck do not slip from position and pose no flying brand hazard.