What Do Shingle Wind and Impact Ratings Mean?

ASTM D7158, first published in 2005 from wind engineering research, works the other way round. It measures how much suction the wind puts on the shingle and how hard its sealant strip holds, then works out from the two, with the wind design method the building codes rely on, the design wind speed the shingle can resist. Its classes are tied to the code's design wind speeds, which are 3-second gusts, and ARMA says the method has a safety factor of about 1.67 built in.

California's residential code requires D7158, with the class printed on the package, and allows D3161 only for shingles that D7158 doesn't cover (CRC R905.2.4.1). D7158's classes assume a building no taller than 60 feet, a site that isn't directly exposed to wind off open water, and no speed-up from hills. For a house outside those assumptions, such as one facing the ocean or on an exposed ridge, the code calls for additional calculations; ARMA's 2026 bulletin gives a table for exposure and height and notes that a hill's speed-up often calls for a higher class.

For most re-roofs, the label settles it. A shingle labeled D7158 Class H, or D3161 Class F, meets every row of the code's table, up to 194 mph, and the Department of Energy's guide to shingle roofs notes that many manufacturers rate whole product lines Class H or F, including 3-tab, architectural and premium shingles. The four flagship architectural shingles in shingle brands compared all list both.

The code also sets the nails: at least four per strip shingle, or more where the maker's instructions call for them, and galvanized steel, stainless steel, aluminum or copper roofing nails with a 12-gauge shank and a 3/8-inch head, long enough to go 3/4 inch into the deck or through it (CRC R905.2.5 and R905.2.6).

On the mountain ridges the wind reached 98 to 100 mph; at the valley and coastal stations in the table, 48 to 84 mph. That's below the 110 mph of the Class F fan test and the 116 mph design speed that even Class D covers, but the numbers don't compare directly: a gust lasts seconds, the fan test runs for two hours, and both wind ratings assume shingles that have sealed and are nailed the way the maker specifies.

• Sealing. The sealant strip is activated by the sun's heat. IBHS says manufacturers recommend 70 to 80°F for sealing and warn that below 40°F shingles may not seal properly; a roof can seal in one to two weeks in summer but can take one to two months or more in less favorable conditions, and until then wind can lift the shingles. A roof put on in late fall or winter can meet its first Santa Ana before it has fully sealed.
• Edges and ridges. Starter strips with a line of sealant run along the eaves and up the rakes, where they protect against uplift at the roof edges, and hip and ridge caps are nailed on each side above their sealant strip.
• Nails. The Department of Energy's guide calls improper nailing one of the common installation errors: nails placed too high or too low, overdriven, underdriven or angled. For high-wind areas it recommends six nails per shingle, placed in the nailing zone, and roof cement under the shingles along the eaves, rakes, hips and ridges.
• The warranty's terms. Wind warranties step up with the same details. Owens Corning's Oakridge, for example, goes from 110 mph with four nails to 130 mph with six nails and its starter shingles at the eaves and rakes, as covered in architectural vs 3-tab shingles; what wind warranties exclude is in roofing warranties explained.
• Age. A rating from the day the roof went on doesn't describe it 20 years later. Missing tabs after wind on an old roof are a reason to look at the whole roof, as in signs you need a new roof.

Large hail is rare here. NOAA's Storm Events Database lists 23 hail reports in Los Angeles County from 1996 through 2025, on 17 days. The largest stone reported was 1.75 inches, in Leona Valley in October 2015; four reports were 1.25 inches or more, and none reached 2 inches. The most recent were in March 2024, up to an inch, in places including Granada Hills and Azusa.

So in Los Angeles, Class 4 is a choice rather than a requirement. ARMA notes that impact ratings may lower insurance costs in some areas and with some insurers; ask yours whether it gives a discount in California before paying more for that reason. Other roofs are sold as Class 4 as well, including stone-coated steel and synthetic slate and shake.

1. What the wind warranty asks for. The number of nails, the maker's starter strips at the eaves and rakes, its hip and ridge caps and any other accessories, by name.
2. An exposed site. A ridge-top or oceanfront house is outside D7158's standard assumptions, and canyons can have unusual winds; ask how the class and the nailing were chosen.
3. The impact class, if you want one. UL 2218 or FM 4473 Class 4, and whether your insurer gives anything for it.
4. The fire class. Wind and impact ratings say nothing about fire; the Class A roof rating is a separate test.
5. The season. On a roof going on in the cool months, ask how the shingles will be sealed, following the maker's instructions.

Code sections, rules and figures on this page come from the primary sources below. Codes, local requirements and product terms change; each was verified October 8, 2026.

1. California Residential Code 2025, Chapter 9, Roof Assemblies (R905.2.4.1 and Table R905.2.4.1, R905.2.5, R905.2.6)
2. California Residential Code 2025, Chapter 3, Building Planning (Figure R301.2(2) and its notes, R301.2.1.4)
3. Asphalt Roofing Manufacturers Association, Asphalt Shingle Product and Test Standards
4. Asphalt Roofing Manufacturers Association, Technical Bulletin: Using ASTM D7158 Where Standard Conditions Do Not Apply (March 2026)
5. Insurance Institute for Business & Home Safety, Roof 101
6. Mark S. Graham, NRCA, "The wind resistance of shingles," Professional Roofing, September 2018
7. Anne Cope and Ian Giammanco, IBHS, "Hail no!," Professional Roofing, March 2022
8. U.S. Department of Energy, Building America Solution Center, Asphalt Shingle Roofs
9. National Weather Service Los Angeles/Oxnard, Public Information Statement, 5:53 a.m. PST January 8, 2025 (highest wind reports, past two days),…
10. Tom Murphree, Emily Szasz and Kellen Jones, Santa Ana Events in California, NOAA National Weather Service Science and Technology Infusion Climate…
11. NOAA National Centers for Environmental Information, Storm Events Database, annual detail files 1996–2025 (hail, Los Angeles County)
12. DECRA Roofing Systems, Product Knowledge: Hail, Understanding Impact Resistance (UL 2218 classes)