How Long Does A Roof Have To Be Fire Resistant

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.

How long does a roof have to be fire resistant.

According to the engineered wood association a one hour rating indicates that a wall constructed in a manner similar to the one tested will contain flames and high temperatures and support its full load for at least one hour after the fire begins. The intermittent flame test. Class b fire retardant treatment is effective against moderate fire exposures. 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. Note that underwriters laboratories has had a fire resistance test for roof coverings including shingles since 1958. 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. Some building jurisdictions now require a fire watch for a minimum of one hour after the last roofing torch has been extinguished.

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. Fire resistance ratings time temperature include structural elements and everything above including the roof membrane and its surfacing. For example an office that is less than 18m tall must maintain structural stability for 60 minutes during a fire. 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.

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. During construction there are many opportunities for accidental ignition including welding of steel and the use of torches on modified bituminous roof membranes. Fire resistance ratings are expressed in the number of minutes or hours a structure can withstand a fire simulation test. If you have one of these roofing types you might want to look into replacing the roofing material for a more fire resistant option.

To meet class a the test specimen must resist 15 cycles class b eight cycles and class c three cycles. Asphalt shingles class a asphalt shingles can withstand a fire burning through the wooden structural components for up to two hours. As many people know wood is fuel for a fire despite the fact that it is a valuable and reliable roofing material.