Hail is part of life in Winnebago and Boone counties. Most summers bring at least a few nights of strong storms, and every homeowner here has seen a neighbor’s roof get replaced after one of them.
So when it’s time for a new roof, a lot of people ask the same question: should I pay more for Class 4 impact-resistant shingles? Here’s a straight answer, including what the rating means, what it doesn’t, and who it makes the most sense for.
What “Class 4” actually means
Class 4 is the top rating in a lab test called UL 2218. It measures how well a roofing product holds up to being hit.
Here’s how the test works. Under UL 2218, a steel ball is dropped twice on the same spot from a set height. GAF explains it this way: a shingle that withstands a 1.75-inch ball dropped from 17 feet earns Class 3, and one that withstands a 2-inch ball dropped from 20 feet earns Class 4, the highest rating.
Two things are worth knowing about that test:
- It’s a lab test, not a hailstorm. Real hail varies in size, density, speed and angle. The rating tells you how a shingle compares to others under the same conditions. It doesn’t promise how it will do in a specific storm.
- Only rated packaging counts. GAF notes that a product is Class 4 rated only when it’s sold in packages carrying the UL 2218 Class 4 statement. Ask to see it.
How Class 4 shingles are different
Standard architectural shingles are built on a fiberglass mat coated with asphalt and granules. Impact-rated shingles change that recipe in one of two ways.
Rubber-modified asphalt. Some Class 4 shingles use SBS-modified asphalt, a polymer blend that makes the shingle more flexible, a bit like rubber. When something hits it, the shingle gives instead of cracking. GAF uses this in Timberline AS II and Grand Sequoia AS. GAF also says this formula lets shingles lie flatter in cooler weather than its standard shingle, which is a nice bonus in a Stateline fall.
A stronger mat. Others reinforce the core of the shingle. GAF’s Timberline UHDZ uses its UltraMat technology to reach a Class 4 rating.
For comparison, GAF lists its popular Timberline HDZ as a Class 3 shingle. That’s a solid rating on its own, and it’s the shingle most families pick. Class 4 is a step up from there.
What impact-resistant shingles can do
- Resist cracking and bruising. Ordinary shingles hit by hail can crack, or get “bruised,” where the mat breaks under the surface and granules loosen. Over time, bruised spots wear faster and can leak. A Class 4 shingle is built to take more of that punishment before it breaks.
- Hold up to other impacts. Falling branches, acorns and debris thrown by high winds hit roofs too. The same toughness helps there.
- Look like a normal roof. Today’s impact-rated shingles look like regular architectural shingles. Your neighbors won’t know the difference.
What they can’t do
It’s important to be honest about the limits.
- They aren’t hail-proof. Very large hail can still damage any shingle, rated or not.
- Hail isn’t covered by the shingle warranty. GAF states that it makes no warranty about how its shingles perform against hail, and that hail damage is not covered under its limited warranty. That’s true for its impact-rated lines too. The rating is about toughness, not coverage.
- They don’t fix other roof problems. Poor attic ventilation, worn flashing or soft decking will still cause trouble under a Class 4 shingle. The whole roof system has to be done right. For other ways to get your home ready for storm season, see our tips to protect your Rockford home from storm damage.
So, are they worth it here?
For a lot of Northern Illinois homes, yes. But it depends on your situation. Class 4 shingles make the most sense if:
- Your roof has already been damaged by hail once or more. If it happened before, it will probably happen again.
- You plan to stay put for a long time. The longer you own the home, the more storms the roof has to get through.
- Your home sits in the open. Homes on the edge of farmland or on a hill, with no big trees or neighboring houses to block the wind, take more direct hits.
- You want fewer surprises. Some people just want the toughest shingle they can get so they worry less every time the sky turns green.
A standard architectural shingle can still be the right choice if:
- You plan to sell in the next few years.
- Your budget is tight and the difference would mean putting off a roof that needs to be replaced now. A properly installed standard roof is far better than a failing one.
- Your home is well sheltered by mature trees and nearby houses.
Impact-rated shingles cost more upfront than standard ones. At your free inspection, we’ll go over both, along with which GAF warranty your roof qualifies for, so you can decide what’s worth it for your home. We also install metal roofs on homes if you’d like to compare.
Questions to ask your roofer
- Is this exact shingle UL 2218 Class 4 rated, and does the packaging say so?
- What’s the price difference compared to the standard shingle you’d otherwise install?
- Which accessories (starter strip, underlayment, leak barrier, ridge cap and ventilation) come with the system?
- What warranty covers the shingles, and what warranty covers the workmanship?
How Martin Exteriors can help
We’ve been roofing homes across the Stateline since 2006. As a GAF Master Elite contractor, a status fewer than 2% of roofing contractors earn, we can offer a 50-year GAF warranty with 30 years on workmanship on qualifying roofs (GAF eligibility rules apply). Every roof also comes with our workmanship warranty, and most roofs are done in a day.
If your roof already has hail damage, see our hail damage repair page. If you’re planning a roof replacement, ask about impact-rated shingles at your free inspection. Financing is available as low as $149/month for qualified buyers.
For the GAF shingle lines we install most and real shingle projects, see our asphalt shingle roofing page.
Schedule a free roof inspection or call (815) 624-6278. We’re open 24/7.
Frequently Asked Questions
What is a Class 4 impact-resistant shingle?
It’s a shingle that earned the highest rating, Class 4, in the UL 2218 impact test. In that test, a 2-inch steel ball is dropped from 20 feet twice in the same spot, and the shingle must not crack through.
Are Class 4 shingles hail-proof?
No. They’re built to resist cracking and bruising better than standard shingles, but very large hail can still damage them. GAF also states that hail damage is not covered under its shingle warranty.
Do Class 4 shingles look different from regular shingles?
Not really. Modern impact-rated shingles look like standard architectural shingles and come in similar colors.
Is GAF Timberline HDZ a Class 4 shingle?
GAF lists Timberline HDZ as Class 3. GAF’s Class 4 options include Timberline AS II, Timberline UHDZ and Grand Sequoia AS. Check the packaging for the UL 2218 Class 4 statement.
Are impact-resistant shingles worth it in Northern Illinois?
They often are if your roof has been hit by hail before, your home sits in the open or you plan to stay for many years. If you’re selling soon or the budget is tight, a properly installed standard architectural shingle can be the better choice.
