What the classes mean

The rating comes from a lab test called UL 2218. A steel ball is dropped onto the shingle, and the tester checks the back of the shingle for cracks.

  • Class 3: a 1.75 inch steel ball dropped from 17 feet
  • Class 4: a 2 inch steel ball dropped from 20 feet

To pass, the shingle can dent, but it cannot crack through. Class 4 is the highest rating the test gives.

Which shingles are which

Owens Corning Duration and GAF Timberline HDZ are rated Class 3.

For Class 4, look at GAF Timberline UHDZ, Timberline AS II, Grand Sequoia, and Grand Sequoia AS, or Owens Corning Duration STORM, Duration FLEX, and Woodcrest. You can see their colors on our shingle color picker.

What Class 4 can do for your insurance

Some insurance companies give a discount for a Class 4 roof. It is different for every company, so ask your agent what yours offers before you pick a shingle.

Under a Colorado law signed in 2026, insurance companies will have to report those discounts to the state each year.

What a Class 4 rating does not do

No shingle is hail proof. The rating comes from a lab test, and real storms vary. GAF says hail damage is not covered by its shingle warranties, so hail damage is still a homeowners insurance claim. See roof warranties.

Class 4 shingles or a Fortified roof?

Class 4 is about the shingle. A Fortified roof is about the whole roof: a sealed roof deck, ring-shank nails, locked-down edges, and in hail country, impact-rated shingles, all checked by an independent evaluator.

Sources: GAF, Class 4 shingles; GAF, Class 3 shingles.