Class 4 Impact-Resistant Shingles for Northern Illinois Hail

What a Class 4 rating on impact-resistant shingles proves

UL 2218 is a laboratory test. Technicians drop steel balls onto a shingle assembly from set heights, then look for cracks, tears or splits on the back of the shingle or through the mat. The four classes step up in ball size and drop height:

• Class 1: a 1¼-inch ball from 12 feet
• Class 2: a 1½-inch ball from 14 feet
• Class 3: a 1¾-inch ball from 17 feet
• Class 4: a 2-inch ball from 20 feet

The drops are aimed at weak points such as edges and the joints between shingles. Marks on the top surface do not count as a failure. Some products also list a Class 4 result under FM 4473, a separate test that fires ice balls instead of steel. Both tests use new product, so neither tells you how a shingle will behave after fifteen summers of sun.

Rubberized asphalt or reinforced backing: two routes to Class 4

Manufacturers reach Class 4 in two main ways, and some combine them.

Polymer-modified asphalt. Blending a polymer such as SBS (styrene-butadiene-styrene) into the asphalt makes it behave more like rubber. A hailstone pushes the shingle in and it rebounds instead of fracturing. Owens Corning’s Duration FLEX and GAF’s Timberline AS II are SBS lines. TAMKO’s StormFighter impact-resistant line also uses a polymer-modified asphalt, and Malarkey’s Legacy and Vista are polymer-modified (rubberized) asphalt shingles. A practical bonus in our climate is that these shingles stay flexible in the cold.

Reinforcement. Other designs bond a tough polymer mesh or fabric to the back of a conventional shingle so it holds together instead of splitting when struck. They can pass the same test, but the asphalt itself is no more flexible than a standard shingle’s.

Neither label tells the whole story. Look up the UL 2218 listing for the exact product on your quote.

IBHS ratings: why two Class 4 shingles can still differ

Because UL 2218 is pass or fail, two Class 4 shingles can behave quite differently in a real storm. The Insurance Institute for Business & Home Safety (IBHS), an insurance-industry research organization, tests impact-rated shingles in its own lab and scores them for dents, tears and granule loss on a scale from Poor to Excellent. In its 2025 update, 18 of 23 products rated Good, five rated Marginal and none earned Excellent overall. IBHS’s FORTIFIED program accepts only Good or Excellent shingles for its hail supplement.

The list changes as products are reformulated, so check the current version before you choose. When you request a roof replacement estimate, ask for the impact-rated option to be priced as its own line, so you can see exactly what the upgrade costs on your house.

How often hail matters on a Chicago-area roof

Hail here is patchy. The Illinois State Water Survey puts the long-term average at roughly two hail days a year at any one location, and many storms drop stones too small to harm a sound roof. The trouble comes from a few intense cells. On March 10, 2026, a supercell dropped hail of about two inches, and locally up to four, across Bolingbrook, Woodridge, Downers Grove, Westmont and Darien. That was early in a severe-weather season that normally stretches from spring into late summer.

So the useful question is not whether your street will see hail this year. It is how many years your next roof has to stay sound, and whether your block has already been through repeated claims. If your current roof was replaced after hail once already, a Class 4 product is easy to justify. Our storm damage repair page covers what to do in the first days after a storm.

Insurance credits: ask your agent before you buy

Some insurers lower premiums for a roof with a qualifying impact rating. Others do not, and the amount varies by company and policy. No contractor can tell you what your carrier will do, so be wary of anyone who quotes a savings figure. Before you sign, ask your agent four things:

1. Does my policy offer an impact-resistant roof credit, and how large is it?
2. Which rating qualifies: UL 2218 Class 4, FM 4473 Class 4, or either?
3. What proof do you need: an invoice, a product listing, photos or a form?
4. Does the credit add a cosmetic-damage exclusion, and what would that mean for surface marks that don’t affect how the roof sheds water?

That last question matters. A credit paired with a cosmetic exclusion can be a fair trade, but make it knowingly. Your insurer makes the coverage decision; our part is clear documentation and a line-item scope. More on that in our hail and wind insurance guide.

How it handles Chicago-area weather

Care and maintenance

Care for a Class 4 roof the way you would any shingle roof: keep gutters clear, trim branches back, and never pressure-wash. The difference is what you do after a storm. Walk the yard first. Dented downspouts, gutter screens and window wraps tell you roughly how large the hail ran. If the stones were an inch or bigger, have the roof checked even if nothing looks wrong from the ground, and photograph the soft metals before anyone repairs them. Keep the invoice and the product name in your house file so you can show your insurer which rated shingle is on the roof.

Impact-Resistant (Class 4) Shingles: common questions

Do Class 4 shingles look different from regular shingles?

No. From the curb they look like any dimensional shingle, and manufacturers offer them in a broad palette. The difference is in the asphalt formula and the backing, not the surface.

Are Class 4 shingles hail-proof?

No roof is hail-proof. The rating means the shingle passed a 2-inch steel-ball test when new. Bigger stones, wind-driven hail and years of UV exposure can still cause damage, so keep checking the roof after major storms.

Can I put impact-resistant shingles on only the damaged slope?

You can, but the slope may not match the rest of the roof in color or profile, and an insurer offering a credit will want to know what covers the entire roof. Ask your agent before mixing products.

Are impact-resistant shingles harder to install in cold weather?

Polymer-modified shingles are generally easier to handle in the cold than standard ones because they bend without cracking. Their sealant strips still need warmth to bond, so a late-fall install may call for hand-sealing as the manufacturer’s instructions describe.