Class 4 Shingles: UL 2218, FM 4473, IBHS Ratings and Discounts

Class 4 test: 2 in steel ball from 20 ft
Tile and slate: FM 4473 ice-ball classes
Field ratings: IBHS: Excellent, Good, Marginal, Poor

What do UL 2218 Classes 1 to 4 mean?

Each class drops a steel ball twice on the same spot; the sample fails if it cracks or opens (inspected from the back).
Class	Steel ball diameter	Drop height
1	1.25 in	12 ft
2	1.5 in	15 ft
3	1.75 in	17 ft
4	2.0 in	20 ft

Only cracks or openings count as failures. Dents, bruise marks and granule loss do not, so a Class 4 shingle can still look damaged after a storm.

How are tile and slate rated?

FM Approvals standard 4473 tests rigid roofing such as tile and slate with frozen ice balls instead of steel:

Class	Ice ball diameter	Target impact energy
1	1.25 in	3.72 ft-lb
2	1.5 in	7.77 ft-lb
3	1.75 in	14.95 ft-lb
4	2 in	26.81 ft-lb

What are IBHS shingle ratings?

The Insurance Institute for Business and Home Safety (IBHS) rates impact-resistant shingles as Excellent, Good, Marginal or Poor using laboratory hailstones made to behave like natural hail, a tougher test than steel balls. Products must already be UL 2218 certified to take part (a joint UL and IBHS program announced in 2023). In the fourth edition of the ratings (November 19, 2025), 24 products were rated; most were Good and none was rated Excellent. The FORTIFIED Home hail supplement requires shingles rated Good or Excellent.

Do Class 4 roofs lower insurance premiums?

Sometimes, depending on the state and the insurer. Programs we could verify:

State	What applies
Texas	Mandatory premium credits for UL 2218 roofs since 1998 (TDI Bulletin B-0024-98); the amount is set company by company. Labels must show the class, manufacturer and year manufactured.
Minnesota	Premium discount required for homes with a FORTIFIED roof designation that includes the hail supplement (Minn. Stat. 65A.298); Class 4 alone does not qualify.
Kentucky	FORTIFIED discounts required if actuarially justified, for policies issued or renewed on or after March 1, 2026.
Alabama	FORTIFIED discounts on the wind portion of the premium (wind-oriented).
Colorado	SB26-155 (signed June 4, 2026) funds hail-resilient roof grants and requires insurers to report resilient-roof discounts; it does not mandate a discount.
Oklahoma	Strengthen Oklahoma Homes grants of up to $10,000; no statutory discount mandate found.

Elsewhere, ask insurers directly; many offer voluntary discounts.

Are Class 4 shingles worth it?

In hail-prone areas they reduce the chance of functional damage from mid-size hail, may lower premiums, and can qualify for grants. They cost more than standard shingles, still dent and lose granules, and very large hail can break them. Check what your insurer credits, and whether your jurisdiction or a grant program has its own requirements. See what size hail damages a roof.

Frequently asked questions

Are Class 4 shingles hail-proof?

No. They passed a 2-inch steel-ball test without cracking, but larger hail can still break them, and dents and granule loss are not counted in that test.

How do I know if my roof is Class 4?

Check the installation records or the shingle wrapper label. In Texas, impact-resistant roofing labels must show the class, manufacturer and year manufactured, and contractors file a TDI form to document it for insurance credits.

Is Class 4 the same as FORTIFIED?

No. FORTIFIED is an IBHS construction standard for the whole roof system; its hail supplement requires shingles rated Good or Excellent by IBHS, which is stricter than UL 2218 Class 4 alone.

Class 4 impact-resistant shingles explained