Two Rating Languages You See
Most of the confusion comes from mixing up test ratings with warranty language.
Hail ratings are usually impact-resistance classes from standardized testing. Wind ratings are usually ASTM test classes. Wind warranties are separate. They’re written in mph and often depend on the full roof system and install details.
Hail Ratings And What UL 2218 Measures
UL 2218 is the common impact test you’ll hear about for hail. Shingles earn Class 1 through Class 4, with Class 4 at the top of that scale. The test uses steel balls dropped from set heights to match impact energy.
Here’s the catch. UL 2218 focuses on breach-type damage seen from the back side. It does not fully capture surface issues like dents and granule loss.
IBHS Ratings Add Another Layer
IBHS built a different hail testing approach using lab-made ice spheres and damage scoring that includes things homeowners actually see, including granule loss. IBHS then publishes ratings like “Good” and “Excellent,” and recent updates added a numerical score for more transparency. Lab results still can’t promise identical field results on every roof, in every storm.
Wind Ratings Versus Wind Warranties
Wind test ratings usually show up as ASTM classes. ASTM D3161 is a fan-induced method that’s commonly shown as Class A, D, or F. ASTM D7158 is an uplift-force method that’s commonly shown as Class D, G, or H.
Then you’ll see a separate wind warranty in mph. That mph number can be “upgradeable” if the manufacturer requires specific starter shingles and hip and ridge products. So, the highest wind rated shingles on paper are the ones with strong ASTM classes and a wind warranty that matches the system you’re actually installing.
What Really Controls Storm Performance
A rating is a starting point. Real performance comes down to the roof system and the install.
Here are the details we pay attention to on every job:
- Nail placement and nail count, since misnailing can drop wind performance fast.
- Starter strips, hip and ridge caps, and the accessory combos tied to the wind warranty language.
- Seal-down behavior, since wind uplift and blow-offs track back to how well shingles bond.
- Deck and underlayment choices, especially on low slopes and details that see water backup.
- Steep-slope fastening patterns, since some systems call for extra nails and adhesive spots.
If you’re comparing the best asphalt shingles for high wind, ask for the exact ASTM class and the exact warranty requirements in writing. Then match that against your roof shape and pitch.
Picking Shingles For Knoxville Weather
Knoxville storms can bring hail and straight-line wind. The National Weather Service uses 1-inch hail and 58-mph gusts as a severe baseline. Higher tags kick in at larger hail and stronger gusts.
That’s why we talk through both sides of the label. If you’re worried about hail damage on asphalt roof shingles, look at UL impact class, then check IBHS ratings if you want a second filter. If wind is the bigger fear, focus on wind damage architectural shingles and confirm the ASTM class plus the install system needed for the wind warranty you want.
If you’d like a deeper look at materials, start with our asphalt shingle roofing options. If you want a local pro to walk the specs with you, here’s our Knoxville roofing contractor page.
A Clear Plan Before The Next Storm
We’re a small Knoxville team, and Brad stays hands-on with quotes and scope. If you want to compare ratings, warranty language, and real install details, take a look at our roofing warranty coverage and what to expect during a roof replacement. Then reach out through our contact Mountain View Exteriors page.