Short answer: Class 3 and Class 4 are UL 2218 impact ratings: Class 4, the highest, is tested with a 2-inch steel ball and Class 3 with a 1.75-inch ball. A rating is a lab result, not a guarantee against hail damage. Some insurers offer discounts for impact-resistant roofs, so ask your insurer.
Class 3 and Class 4 are lab ratings for how well a roofing product takes a hit. Below are the two ratings side by side, what the tests check, and what they leave out. Whether Class 4 is worth it on your home is a separate question, covered in Class 4 impact-resistant shingles in Colorado.
What is the difference between Class 3 and Class 4 shingles?
The size of the test ball. Two lab standards rate impact resistance: UL 2218 drops steel balls on the product, and FM 4473 uses ice balls. Each has four classes. A Class 3 product is tested with a 1.75-inch ball and a Class 4 product with a 2-inch ball, the largest in both standards.
| Test | Class 3 | Class 4 | Source |
|---|---|---|---|
| UL 2218 steel ball | 1.75 in, dropped 17 ft | 2.00 in, dropped 20 ft | PRI Group (UL 2218 table); IBHS, 2014 (PDF) (diameters) |
| FM 4473 ice ball | 1.75 in | 2.00 in | PRI Group (FM 4473 table) |
| Pass condition | No evidence of cracking (UL 2218); no breaking or visible cracking (FM 4473) | Same as Class 3 | PRI Group |
| Highest rating? | No | Yes, the top of 4 classes | PRI Group; IBHS, 2014 (PDF) |
In IBHS's UL 2218 testing, each test spot took two strikes from the ball. Sources checked Oct 15, 2026.
What do UL 2218 and FM 4473 not measure?
Mostly, they check for cracks. In its 2014 paper, IBHS explains that UL 2218 counts a failure only when an opening (a tear, fracture, crack or rupture) shows on the back of the shingle. Dents, crushed or loose granules, and marks that show only on the top do not count as failures. So a shingle can pass with dents or granule loss on its surface.
The Insurance Institute for Business & Home Safety (IBHS) runs a different test. It uses lab-made hailstones instead of steel balls and scores dents, tears and granule loss. Products are rated Excellent, Good, Marginal or Poor. Its 2025 ratings covered 24 products, about 95% of the impact-resistant shingles sold each year. None rated Excellent; most rated Good (IBHS release, Nov 19, 2025). The product-by-product results are at ibhs.org/ImpactRatings.
For what Class 4 can and can't do on a real roof, and when it's worth the upgrade, see Class 4 impact-resistant shingles in Colorado.
Do Class 4 shingles get you an insurance discount in Colorado?
Some insurers offer premium discounts for impact-resistant roofs. Ask your insurer or agent what qualifies. The Colorado Division of Insurance (DOI) gives the same advice: in a May 31, 2024 consumer advisory, the Insurance Commissioner told homeowners replacing a hail-damaged roof to ask their insurance company or agent what premium discounts may be available for hail-resistant material.
The DOI has also found that hail damage is the number one cost driver of homeowners insurance premiums in Colorado, accounting for an average of 26 to 54 percent of an annual premium (DOI release, June 4, 2026). The same release announces SB26-155, which creates a state grant program to help homeowners upgrade their roofs against hail. The law does not mention Class 4 shingles; here's what SB26-155 actually does.
We're a roofer, not a public adjuster, so we talk about the roof, not the policy.
Further reading
- For another view: the Colorado Roofing Association's Class 3 vs Class 4 shingles for Colorado homes.
- A benefit-cost analysis of impact-resistant asphalt shingle roofing (PDF), Keith Porter, March 2022, for Canada's Institute for Catastrophic Loss Reduction. It studied Calgary, Canada, not Colorado.
If you want a second look at your roof, book a free inspection. If it's fine, we'll say so.