Factory Mutual Testing for Commercial Roofing

In the world of commercial roofing, no approval is more important than Factory Mutual.

Factory Mutual (FM) was originally conceived as a testing laboratory dedicated to reducing insurance claims by creating performance standards for building products to address the costliest causes of building damage. For commercial roofing systems, there are three major areas of concern – fire damage, wind damage and hail damage.

There are buildings throughout the world that are insured by a Factory Mutual affiliate, and for these buildings, the use of Factory Mutual-approved products is required unless the building owners are willing to pay much higher insurance premiums, and most are not.

Although Factory Mutual still claims that it does not establish industry performance standards and is only an insurance laboratory, building specifications are written all the time requiring Factory Mutual approval for 
buildings not insured by a Factory Mutual affiliate.

FM is the standard everyone uses.


commercial roofing fire test

Factory Mutual tests commercial roofing assemblies (including vapor barrier, insulation, coverboard and membrane) in accordance with ASTM E108. This test consists of 8-foot long, 1-meter wide test samples that are set at a specific slope and then subjected to 10 minutes of fan-blown gas flames that eventually start the roof assembly burning at one end. The flame spreads up the roof assembly sample until the 10 minutes are over.

Class I (A)

Less than 6 feet of flame spread up the roof assembly (This is what everyone wants)

Class II (B)

Less than 8 feet of flame spread up the roof assembly (Satisfies most building code requirements)


Factory Mutual tests commercial roofing assemblies for wind uplift depending upon how the assembly is attached to the structural deck.

For commercial roofing assemblies where all components are adhered together and adhered to the deck, the test consists of a 2-foot by 2-foot sample constructed on a concrete block. A steel and plywood fixture is bonded to the top of the test sample and then subjected to a tensile load that increases every minute by 15 psf until failure – something gives way and the assembly is torn apart.

commercial roofing wind damage

For commercial roofing assemblies where at least one component is secured to the structural deck with mechanical fasteners, the test consists of a 12-foot by 24-foot sample constructed on a steel deck/steel purlin assembly. The assembly is clamped down at the perimeter to create an airtight seal. Pressurized air is introduced into the assembly from the under side of the test table and increases every minute by 15 psf until failure – something gives way and the assembly is blown apart.

FM-supplied tables are available that provide the required uplift pressure resistance for a specific building. These tables take into consideration the building height, design wind speed based upon geographical location, and surrounding terrain. A safety factor of 2:1 is incorporated, i.e., a 90 psf test rating equates to a 45 psf design pressure. Additional considerations are made for increased pressure at the perimeter of the roof, and even higher pressure at the corners of the roof.


Factory Mutual tests commercial roofing membranes for hail resistance by subjecting a membrane sample to the impact of a steel ball (approximately two inches in diameter) that is dropped from a defined height. The weight of the ball and the height of the drop are varied to create two levels of impact energy. The roof membrane passes if the impact locations do not exhibit fracture of the membrane.

Sikalastic RoofPro provides assemblies that meet the Severe Hail requirement

Severe Hail Required in the most hail-prone locations.
Moderate Hail Required in most locations.


The FM RoofNav program provides a means of obtaining a specific Factory Mutual-approved commercial roofing assembly. The RoofNav assembly number is often requested by specifiers as part of the roofing submittal package.

Contact Tech Services to obtain more information regarding RoofNav assemblies.