How the UL 2218 test works
UL 2218 drops steel balls onto a shingle from heights set so each ball hits with the energy of a same-size hailstone. Each spot is hit twice. The shingle fails if the back shows any tearing, fracture, cracking or rupture.
| Class | Steel ball size | Impact energy |
|---|---|---|
| Class 1 | 1.25 in. | 3.53 ft-lb |
| Class 2 | 1.50 in. | 7.35 ft-lb |
| Class 3 | 1.75 in. | 13.56 ft-lb |
| Class 4 (highest) | 2.00 in. | 23.71 ft-lb |
Ball sizes from IBHS; impact energies from NRCA.
Many standard architectural shingles rate Class 3. Most brands also sell a Class 4 line. See them side by side in our shingle brand comparison.
What about FM 4473?
FM 4473 is another impact standard that fires ice balls instead of dropping steel ones. Its scope is rigid roofing like concrete tile, clay tile and slate, so you will mostly see it on tile products rather than shingles.
How well do Class 4 shingles hold up in real storms?
The Insurance Institute for Business & Home Safety (IBHS), which tests roofs with lab-made hail, has found that many impact-resistant shingles do not perform as expected in real-world storms. The label is a useful floor, not a guarantee.
Is Class 4 worth it in Florida?
- Hail is less common here. NOAA says Florida has the most thunderstorms of any state, but Nebraska, Colorado and Wyoming usually have the most hailstorms.
- Insurance credits are not required by law. Florida’s wind-mitigation discount law (s. 627.0629) covers wind features like roof deck attachment, roof-to-wall connections and opening protection. It does not mention hail or impact ratings. Some insurers may still give a credit, so ask yours in writing.
- Debris. Hurricanes throw branches and debris, and a tougher shingle may resist some of it. We found no Florida study that measures this benefit.
If your insurer confirms in writing a credit that covers the price difference, Class 4 can pay for itself. If not, better nailing, a sealed roof deck and a top wind rating usually do more for a Florida roof.
Compare impact-resistant and standard shingle prices
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Frequently asked questions
What does Class 4 mean on a shingle?
It means the shingle survived two hits from a 2-inch steel ball dropped from a height that matches the energy of a 2-inch hailstone, with no cracking on the back. It is the highest UL 2218 rating.
Do Florida insurers have to discount Class 4 shingles?
No. Florida’s required discounts cover wind-mitigation features. Hail and impact ratings are not listed, though some insurers may offer a credit on their own.
Is Class 3 good enough in Florida?
For most Florida homes, yes. Hail is less frequent here than in the Plains, and wind features matter more for Florida roofs.
More on how roofs work
- How asphalt shingles are made, and why Florida sun wears them out
- Shingle wind ratings explained: what Class F and Class H really mean
- Black streaks on your roof: what they are and how to get rid of them
- Underlayment and secondary water barriers: the layer that saves your house
- How hurricanes damage roofs, and what keeps yours on
- Metal roofing near the coast: Galvalume, aluminum and salt air
- Concrete tile roofs explained: how they are made and what fails first
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