When did impact-resistant shingles come out?
How the rating started
Before the mid 1990s there was no common way to compare how roofing stood up to hail. Underwriters Laboratories, working with the insurance industry, developed UL 2218, which drops steel balls from 1 1/4 to 2 inches in diameter onto roofing samples from set heights. A product that survives the 2-inch ball without cracking through earns Class 4, the top rating.
How the products evolved
- Early Class 4 shingles leaned on SBS polymer-modified asphalt, which flexes instead of fracturing.
- Insurance discounts in hail-prone states pushed demand, and manufacturers added Class 4 lines alongside their standard architectural shingles.
- Newer designs use reinforced backings and mats. For example, GAF's Timberline UHDZ with UltraMat is Class 4, while its Timberline HDZ is Class 3 on labeled packages.
- Newer testing. Critics noted steel balls do not behave like hailstones, and the Insurance Institute for Business and Home Safety has since developed ratings using laboratory-made ice hailstones that also look at granule loss and denting.
Does your roof have them?
If your roof is older or was installed as a standard builder-grade roof, it almost certainly is not Class 4. Check the invoice, the warranty registration, or a leftover bundle wrapper. Insurers that discount impact-resistant roofs typically want that documentation.
The Georgia angle
North Georgia sees regular spring hail. A Class 4 roof does not make you hail-proof, but it improves the odds a moderate storm leaves the roof intact.
More in impact-resistant shingles in Georgia and Georgia hail season, and check your zip code's history at the North Georgia Hail Map.