Illinois Roofing License IDFPR #19HC00108700 · GAF Certified Contractor
Every architectural asphalt shingle sold in the US carries a wind uplift rating – Class A, F, G, or H. The number indicates how much wind speed the shingle is rated to withstand before the seal strip fails and shingles start lifting off the deck. For Illinois homes – which sit in an active wind corridor – the rating that goes on the roof is one of the more consequential spec decisions in a replacement project.
What wind uplift testing actually measures
Asphalt shingle wind ratings come from two standard test methods:
ASTM D3161 – older standard. Mounts shingles on a deck and blows air at increasing speeds for 2 hours per speed level. Pass criteria: no shingles lift more than slightly from the deck.
- Class A – 60 mph (essentially no wind warranty)
- Class D – 90 mph
- Class F – 110 mph
ASTM D7158 – newer (2008+) and more rigorous. Tests for the full structural integrity of the seal strip under sustained wind. Most premium shingles today carry D7158 ratings:
- Class D – 90 mph design wind speed
- Class G – 120 mph design wind speed
- Class H – 130 mph design wind speed
Class H (D7158) is the highest rating commonly available on residential asphalt shingles. Almost all current premium architectural lines hit Class H – GAF Timberline HDZ, CertainTeed Landmark, Owens Corning Duration.
Wind speeds Illinois actually sees
The IRC-derived basic wind speed for Madison County is approximately 115 mph (3-second gust). This is the design wind speed for new construction in the IRC – the speed an engineered structure is required to handle.
In practice, IL homes see:
- Annual peak wind events – 50-70 mph thunderstorm gusts, common multiple times per summer
- Severe thunderstorm events – 75-95 mph straight-line wind (derechos, severe squall lines). Madison County sees one or two of these in most years.
- Tornadoes – EF0 (65-85 mph) and EF1 (86-110 mph) tornadoes occasionally; larger tornadoes are rare but possible
- Major events – the 2023 IL derecho hit 90-100+ mph across much of the state
Shingles rated 60-90 mph (3-tab, low-tier 3-tab) fail at the second tier of events. Class F (110 mph) handles routine severe weather but is marginal at major events. Class H (130 mph) handles essentially everything residential roofing in IL needs to handle.
Why the seal strip matters more than the test
The wind rating tests measure new shingles in lab conditions. Real-world wind performance depends on something the lab test only proxies for: the seal strip.
Every asphalt shingle has a thin strip of factory-applied adhesive on the underside. When shingles are installed and exposed to a few warm sunny days, the seal strip melts onto the shingle below, bonding the two together. This seal is what actually keeps shingles from blowing off in wind events.
Common seal strip failures:
- Cold weather install without seal-down time – if shingles are installed in November and a winter storm arrives before warm weather seals them, the bond may never fully form. Always confirm with your contractor that ambient temperatures during install support seal-down (above ~40°F for several days afterward).
- Excess dust on the deck – if the deck wasn’t swept before installation, dust can contaminate the seal area and reduce adhesion
- Sealant degradation – over 20+ years, the seal strip can crystallize and lose its bond strength. Old shingles fail in wind events even though they were originally Class H rated.
- Owens Corning SureNail strip – adds a woven fabric reinforcement under the nailing zone, giving stronger seal-strip pull-out resistance than standard shingles
Nailing pattern – six nails vs four
Wind uplift ratings assume the shingles are nailed correctly. Most shingle lines support two nailing patterns:
- Four nails – the standard pattern, supports lower wind ratings
- Six nails – required to claim the highest wind warranty on most lines
The difference is two extra nails per shingle, placed in the nailing zone. For a 2,000 sq ft roof that’s about 1,500 extra nails – a few hours of additional labor.
For Class H wind warranty on most premium architectural lines, the six-nail pattern is required. Skipping the extra nails to save labor voids the warranty even though the installation looks identical from the ground.
Trill Roofing uses the six-nail pattern on every install in our service area. The IL wind environment justifies it.
What this means for your install
For a typical Madison County home replacement:
- Specify a Class H (D7158, 130 mph) shingle line – virtually all premium architectural lines qualify
- Confirm the six-nail pattern is used (ask in writing on the quote)
- Avoid late-fall installs if avoidable (let the shingles seal before winter storms)
- If installing in late fall, ask about hand-sealing – applying additional roofing cement to the seal strip area to lock down each shingle manually
- Pair with synthetic underlayment and ice barrier per IL code
Storm warranty claims hinge on three things: did the wind event exceed the shingle’s rating; was the shingle installed per spec; and was the seal strip properly bonded. Get all three right and the shingles do what they’re rated to do.
Schedule a Trill Roofing free inspection at /free-inspection/ – we’ll talk through the full spec on the quote.
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