Roofing Glossary
UL 2218
UL 2218 is the Underwriters Laboratories test standard for impact resistance of prepared roof coverings — the test behind Class 1 through Class 4 impact ratings. It is how the industry objectively measures hail resistance.
The test drops steel balls of specified sizes from specified heights onto the roofing material, then examines it for cracking, fracturing, or tearing. Class 4 — the highest — requires surviving a 2-inch steel ball dropped from 20 feet without fracturing.
UL 2218 is a material test, not a system test: it rates the shingle itself under lab conditions. Real hail varies in size, density, and angle, so the rating is a comparative measure, not a storm guarantee.
Why It Matters
When you see 'Class 4' on a shingle, UL 2218 is the test that earned it. Knowing the standard exists helps you distinguish tested performance claims from marketing language.
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