Owens Corning Class 4 Shingles: Duration FLEX and STORM

Owens Corning makes two Class 4 shingles: TruDefinition Duration FLEX and TruDefinition Duration STORM. Both carry UL 2218 Class 4, the highest impact rating, and Owens Corning pairs them with its ImpactRidge hip and ridge shingles to complete a Class 4 roof. The standard TruDefinition Duration that most people picture is Class 3, not Class 4. FLEX gets its rating from a rubbery SBS polymer modified asphalt; STORM gets it from a reinforcing backing layer Owens Corning calls WeatherGuard Technology. Owens Corning lists both as regional products, so the first question is whether your supplier stocks them.

We are Patriot Roofing and Restoration in Maumelle. Atlas is our primary shingle line, and we install Owens Corning and just about any other brand on request, for example to match an HOA rule or an existing section of roof. Every Owens Corning fact below comes from owenscorning.com, checked on November 7, 2026. We do not hold any Owens Corning certification or system warranty, and this post is product information, not a ranking.

Which Owens Corning shingles are Class 4?

Owens Corning product	UL 2218 impact class	How it earns the rating (Owens Corning's words)	Availability on Owens Corning's page
TruDefinition Duration FLEX	Class 4	"a proprietary blend of SBS polymer modified asphalt"	Regionally
TruDefinition Duration STORM	Class 4	"Patented WeatherGuard Technology," a polymeric backing used as scrim reinforcement	Regionally
ImpactRidge Hip and Ridge	Required to complete a UL 2218 and/or FM 4473 Class 4 roof system	Pairs with Duration FLEX and Duration STORM	Not stated
TruDefinition Duration (standard)	Class 3	Not a Class 4 shingle	Nationwide

On its Duration Series page, Owens Corning also lists Duration Designer, Duration MAX, Duration Premium, Duration COOL and Duration COOL Plus as Class 3. If a quote just says "Owens Corning Duration," it is a Class 3 shingle unless it names FLEX or STORM.

What Class 4 actually means

UL 2218 is the steel ball test. In its own explainer (January 2024), Owens Corning says a Class 4 shingle has to withstand a 2-inch steel ball dropped multiple times from 20 feet, and then the shingle is turned over and checked for cracks or breaks that could let water through. The lower classes use smaller balls from lower heights:

• Class 4: 2-inch ball from 20 feet
• Class 3: 1-3/4-inch ball from 17 feet
• Class 2: 1-1/2-inch ball from 15 feet
• Class 1: 1-1/4-inch ball from 12 feet

Owens Corning is plain about the limits. It says the test does not guarantee a shingle will resist all weather, that hail damage is excluded from its warranty coverage, and that Class 4 does not automatically mean better wind resistance, because wind is rated separately. That is the right way to think about any Class 4 shingle, whatever the brand: it is built to take hits better, not promised to survive every storm. For how hail actually damages a roof, see how hail damages asphalt shingles in Central Arkansas.

Duration FLEX: the flexible one

Owens Corning says the "rubberizing effect" of its SBS modified asphalt makes Duration FLEX pliable, which gives it "greater flexibility and enhanced durability and toughness, especially under intense storm conditions." The idea is that a flexible shingle gives under a hailstone instead of cracking.

• Size. Nominal 13-1/4 by 39-3/8 inches, 5-5/8-inch exposure, 64 shingles and 3 bundles per square, covering 98.4 square feet.
• Wind. Up to 160 mph, which Owens Corning says applies when its component requirements are met and starter shingles are installed on both the eaves and the rakes.
• Algae. Owens Corning says the shingles are algae resistant, and its algae coverage requires an approved Owens Corning hip and ridge product.
• Colors shown. Black Sable, Brownwood, Driftwood, Estate Gray, Onyx Black, Sand Dune, Storm Cloud, Summer Harvest and Teak. Owens Corning notes that products vary by region and recommends seeing a real sample, since screens change colors.

The color list for FLEX is much shorter than the standard Duration list. If you have your heart set on a Duration color, check that it comes in FLEX before you choose the shingle. Our Owens Corning shingle colors post has the full standard Duration list.

Duration STORM: the reinforced one

Duration STORM takes a different route to the same rating. Owens Corning says its patented WeatherGuard Technology integrates a polymeric backing material on the shingle, a scrim reinforcement that "helps the shingle withstand the impact of hail." On the Duration Series page, STORM shares the same headline numbers as FLEX: Class 4, wind up to 160 mph under the same conditions, and 25 years of algae resistance with an approved Owens Corning hip and ridge.

Warranty fine print on both

• Limited Lifetime. Owens Corning lists a Limited Lifetime Warranty on all Duration Series shingles. It covers manufacturing defects, and for a single-family detached home it runs as long as you own the home. It is not a promise about how long the roof will last.
• Hail is excluded. Owens Corning says hail damage is excluded from warranty coverage, even on its Class 4 shingles. Hail damage is an insurance question, not a warranty one.
• Wind has conditions. The 160 mph figure depends on Owens Corning components and starter on eaves and rakes.
• Algae has conditions. The 25-year algae coverage needs an approved Owens Corning hip and ridge, and Owens Corning gives effective dates for it (January 1, 2023 on the Duration Series page, January 1, 2024 on the FLEX page).

Ask your roofer to show you the actual Owens Corning warranty document for the exact shingle in your quote, and who registers it.

Insurance discounts and FORTIFIED

Owens Corning says FLEX and STORM may qualify for a homeowners insurance discount and tells homeowners to check with their insurer. It also points out something many people miss: some insurers require the hip and ridge to be Class 4 too, and some require off-ridge vents. That is why ImpactRidge matters on an Owens Corning Class 4 roof. Before you sign, ask your agent exactly what paperwork they need and whether the ridge counts. Discounts vary by insurer and policy, so treat any discount as "may qualify," never as a sure thing. Our post on impact-resistant shingles and insurance rates in Arkansas goes deeper.

Owens Corning also lists Duration FLEX and Duration STORM as Class 4 options for the hail supplement of the FORTIFIED Roof program, which was developed by the Insurance Institute for Business and Home Safety (IBHS) and is independent of Owens Corning. Owens Corning says using its products does not guarantee a FORTIFIED designation.

How this compares with our Class 4 option

Our Guardian package is built around a Class 4 impact-rated shingle (UL 2218), rated for hail up to 2 inches, and Atlas Pinnacle Impact is the shingle we use in it. Guardian includes impact-rated hip and ridge, so the ridge question above is already answered, plus premium synthetic underlayment, ice and water shield at the eaves, valleys and penetrations, eave and rake starter strips, aluminum drip edge, lifetime pipe flashing and balanced ridge and intake ventilation.

We lead with Atlas for two reasons. First, 3M Scotchgard Protector is factory applied to the Atlas lines we install to fight the black algae streaks so common on humid Arkansas roofs. Second, because we are an Atlas PRO+ contractor at the Gold level installing full Atlas Signature Select systems, an Atlas roof we install and register within 60 days can carry Atlas's extended system warranty covering materials and labor together, with a 15-year premium protection period on Pinnacle Impact. On top of that, a Guardian roof carries our 10-year Patriot Leak Free Guarantee and our 10-year No-Blame-Game Guarantee. If you would rather have Owens Corning FLEX or STORM, we will price it alongside Guardian so you can compare. See every package on our impact-resistant shingle guide and our asphalt shingle roofing page.

Questions to ask before you buy any Class 4 shingle

• Does the bundle wrapper on my roof say UL 2218 Class 4, and which product is it, by name?
• Is the hip and ridge Class 4 too, and does my insurer care?
• Is this shingle stocked locally in the color I want, or is it a special order?
• Which accessories are in the quote, and do they qualify for the maker's wind and algae coverage?
• Does the roofer guarantee the roof will not leak, or only "workmanship"?
• Will I get a written inspection report with photos, and photos of the finished job? (On a full replacement we take 250 to 1,000 photos and send you a link to every one.)

This post is general product information, not insurance advice. Coverage and discounts vary by policy and insurer, so confirm with your agent.

Frequently asked questions

Does Owens Corning make a Class 4 shingle?

Yes, two: TruDefinition Duration FLEX and TruDefinition Duration STORM, both UL 2218 Class 4. Owens Corning pairs them with ImpactRidge hip and ridge shingles to complete a Class 4 roof system.

Is Owens Corning Duration Class 4?

No. The standard TruDefinition Duration is Class 3 on Owens Corning's own page. Only the FLEX and STORM versions are Class 4.

What is the difference between Duration FLEX and Duration STORM?

FLEX uses an SBS polymer modified asphalt that makes the shingle flexible. STORM uses Owens Corning's WeatherGuard Technology, a polymeric backing that reinforces the shingle. Both are Class 4 with the same wind and algae figures on the Duration Series page.

Does the Owens Corning warranty cover hail damage?

No. Owens Corning says hail damage is excluded from its warranty coverage, even on its Class 4 shingles. Hail damage is handled through your homeowners insurance.

Will Class 4 shingles lower my insurance?

They may. Owens Corning says FLEX and STORM may qualify for a discount, and some insurers also require Class 4 hip and ridge or off-ridge vents. Ask your agent before you choose.

Does Patriot install Owens Corning Class 4 shingles?

Yes, on request. Atlas is our primary line, and we do not claim any Owens Corning certification or system warranty.

Want a Class 4 roof priced on your home?

Book a free roof replacement estimate. We measure your roof, give you our 21-point inspection report with photos, and show you all four packages in writing, with Owens Corning FLEX or STORM priced alongside Atlas if you want them.