A b and c designations explain the severity of external fire exposure the roof can withstand.
Fm class 1 roof.
Class 1 is a more rigorous standard.
Because fm approvals requires a 2 1 safety factor roofs with field of roof uplift forces of 30 pounds per square foot are the maximum for 1 60 ratings and 37 5 pounds per square foot are the.
This standard states approval requirements for class 1 panel roofs.
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But not all a b or c are rated as class 1.
Class 1 roofs can substitute for a b or c.
Confusion occurs when roofs are discussed as a b or c and then 1.
Recently the building solutions division of tata bluescope steel announced it received fm approval for its mr 24 standing seam roof system and br 11 roof panel lap seam roof system enabling the firm to provide world class pre engineered building solutions to fm global insured clients and industry investing in india and the saarc south asian association for regional cooperation.
Order to gain a class 1 designation.
All class 1 roof assemblies are class a roofs but not all class a roof systems meet the class 1 rating.
Let s assume that the calculations for our building require a roof that can withstand 23 pounds per square foot of uplift force in the field of the roof.
A class 1 panel roof is one which meets the criteria of this standard for fire wind foot traffic and hail damage resistance.
If any component is utilized in an assembly that is not listed in the respective layer it will nullify the.
For roof areas where the wind rating recommended for the field of the roof does not exceed fm class 1 75 75 pounds per square foot psf 3 6 kpa roof perimeter attachment now is rec ommended to be increased a minimum of 50 percent with at least one fastener per 2 square feet 0 186 m2 and roof corner attachment is recommended to be increased 100 percent with at least one fastener per.
The best rating achieved is class a which is described by ul as effective against severe fire exposure class 1 rating.
The class 1 rating is an exclusive designation that can only be awarded by fm global which indicates the successful testing of the entire roof assembly using fm approval standard 4470.
The standard applies to all components as assembled in the system below the roof cover.
The roof cover is tested in accordance with factory mutual research.
For insulated steel roof deck assemblies fm class 1 includes fm 4470 and fm 4450 approval standard for class 1 insulated steel decks roofs.
While a class 1 assembly can be substituted for a class a b or c roof assembly a class a b or c assembly cannot be substituted for a class 1 roof assembly.
A class i insulated steel roof deck is one which meets the criteria of this standard for fire wind uplift live load resistances corrosion of metal parts and fatigue of plastic parts.
A being severe b moderate and c light.
