What is tested
The standards behind the numbers
A class rating is a result from a lab test on a material sample. It is a useful reference point, not a guarantee about the roof over your head.
Hail impact (UL 2218)
A steel ball is dropped onto the material from 20 feet. The ball size sets the class, and the material must not crack. This is a test of the material, not a prediction for your roof.
Wind resistance
Materials are tested for how they hold up under wind load, which matters most at edges, ridges and fasteners.
Fire rating
Roof covering materials carry a fire classification, from Class A through Class C.
Workplace safety
Falling protection and jobsite practice standards that apply to how the work is carried out on your roof.
Hail impact
How the classes are set
A steel ball is dropped from 20 feet. The ball size sets the class.
- Class 4
- 2 in (51 mm) steel ball dropped from 20 feet. Highest class in the standard.
- Class 3
- 1.75 in (44 mm) steel ball dropped from 20 feet. High impact resistance.
- Class 2
- 1.5 in (38 mm) steel ball dropped from 20 feet. Moderate impact resistance.
- Class 1
- 1.25 in (32 mm) steel ball dropped from 20 feet. Baseline impact resistance.
The same test is run across roofing and surface materials, which is why you will see class numbers quoted in product literature. What your roof actually needs is decided by its material, condition and age.
What we do not claim
References are not warranties
Testing references are not warranties. We do not present a class rating as a promise that a roof will not be damaged by weather, and we do not publish figures we cannot point to a source for. If a number matters to your decision, ask us where it comes from.
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