Class 4 is the highest impact rating a shingle can carry under the UL 2218 test. It is a lab result for one product, not a promise about your roof in a hailstorm. This guide covers what the test does, what it leaves out, which common lines carry the rating, and what to put in a bid.
It does not say what your insurer will do about a Class 4 roof. That is a policy question, so ask your insurer.
What does UL 2218 actually test?
UL 2218 drops steel balls onto the roof covering. UL says the test “results in four ratings — Class 1, 2, 3 and 4 — based on replicating impact energies for natural hailstones by dropping steel balls from various heights” (UL Solutions). IBHS, the nonprofit insurance-industry research group, gives the ball sizes: Class 1 is 1.25 inches, Class 2 is 1.50, Class 3 is 1.75 and Class 4 is 2.00 (IBHS).
GAF puts Class 4 at a 2-inch steel ball dropped from 20 feet, and Class 3 at a 1.75-inch ball from 17 feet (GAF). CertainTeed describes the drops running from 12 feet for the 1.25-inch ball to 20 feet for the 2-inch ball, and says a passing shingle shows “no evidence of tearing, fracturing, cracking, splitting, rupture, crazing, or opening” (CertainTeed).
| UL 2218 class | Steel ball | Drop height |
|---|---|---|
| Class 1 | 1.25 inch | 12 feet |
| Class 3 | 1.75 inch | 17 feet |
| Class 4 | 2.00 inch | 20 feet |
Sources for the table: the ball sizes are from IBHS, and the heights are from GAF and CertainTeed above. Class 2 is a 1.50-inch ball; none of the pages read for this guide gives its drop height, so it is left out of the table.
What a Class 4 label does not promise
This is the part the brochure skips. A pass means the shingle did not crack or tear in the lab. It does not mean hail cannot hurt the roof.
UL itself says the UL 2218 requirements “are based on physical breach damage viewed from the back side of shingles” and “do not account for denting or granule loss damage that a homeowner or insurance adjuster can observe” (UL Solutions, published September 2023). A shingle can pass and still show bruising or bare spots after a storm.
IBHS tested a set of shingles in a 2014 study, including products with Class 4 ratings. It reports that “none of the products tested—basic or impact rated—passed more than Class 2 impacts” when the criterion was no failure at any double-impact location. It adds that the standard tests “do not exactly replicate natural hailstone impacts,” and that its criteria “do not necessarily reflect the performance criteria used by insurance companies” in deciding whether to repair or replace a roof after hail (IBHS). That study is from 2014 and tested the products of that time.
Read it as: Class 4 is a better-than-average test result for that product. It is not hail-proof, and it says nothing about cosmetic damage.
The manufacturer warranty usually excludes hail
Buyers often assume a Class 4 shingle comes with hail coverage. The warranties say the opposite. GAF’s product pages state: “GAF makes no express or implied warranty about the impact performance of this product against hail,” and “Hail damage is not covered under the limited warranty” (GAF UHDZ page). The same two sentences appear on its Class 3 Timberline HDZ page.
IKO’s Cambridge page says: “Damage from hail is not covered under the limited warranty” (IKO). Owens Corning’s shingle warranty lists “Acts of God, such as hail, strong storms or winds (including gusts) over the maximum wind speed listed in the ‘Limited Lifetime Warranty Information Table’” among the conditions it does not cover (Owens Corning warranty, Pub. 10023873-I, August 2026), and that warranty covers Duration STORM.
That is why hail comes back to your homeowners policy, not the shingle warranty. It is also why the next section matters.
Which common shingle lines are Class 4?
Class 4 is a rating on specific products, and sometimes on specific packaging. Here is what the manufacturer pages say, as read in October 2026.
| Line | Impact class per manufacturer | Detail |
|---|---|---|
| GAF Timberline HDZ | Class 3 | GAF says HDZ “pass[es] UL 2218 Class 3.” HDZ is not a Class 4 shingle. Only packages bearing the Class 3 statement are rated (GAF HDZ page). |
| GAF Timberline UHDZ | Class 4 | Only UHDZ sold in packages bearing the UltraMat logo and the UL 2218 Class 4 statement are rated Class 4 (GAF UHDZ page). |
| GAF Timberline AS II | Class 4 | Listed in GAF’s Class 4 group (GAF). |
| Owens Corning Duration STORM | Class 4 | Owens Corning says it meets “UL 2218, Class 4” (Owens Corning). Its literature says the hip and ridge shingle, ProEdge STORM, is “required to complete” the Class 4 roof system (Owens Corning). |
The line to notice is GAF Timberline HDZ, one of the most common architectural shingles on roofs. It is Class 3. A bid that says “GAF Timberline” and nothing more has not told you the class.
CertainTeed says each shingle in its impact-resistant line is Class 4, but the page does not name the products (CertainTeed). If a contractor bids CertainTeed, ask for the exact product name and the Class 4 label for that product.
The insurance angle, and the catch
Some insurers offer a premium credit for an impact-resistant roof. Amounts and eligibility vary by company and state, so ask your own insurer what it offers. Do not assume your insurer offers a credit, or how large it is.
Examples show how it varies. State Farm’s published product listing, last revised October 1, 2026, names Indiana among the places its credits apply. It lists products by standard and class, including ANSI/UL 2218 Class 3 and Class 4. It says only products “bearing the proper certification label are eligible for consideration,” that roofing laid over existing roofing does not qualify (metal is the exception), and that its credits “may qualify” in some states (State Farm). Its consumer page says discount names, percentages and eligibility “may vary by state” (State Farm consumer page).
The Texas Department of Insurance says that for Texas, “A Class 4 roof covering would receive the highest premium credit,” and that the amount “is established by the insurance company on a company-by-company basis” (TDI, as of February 2023). That is Texas rules, not yours.
The catch. GAF warns that “Insurance discounts are not guaranteed,” and that an insurer “may require that you add a cosmetic waiver endorsement to your policy to receive the discount” (GAF). A waiver or exclusion changes what the policy covers, so read the exact wording and ask what it does to a future hail claim. State Farm’s listing makes a signed Cosmetic Damage Exclusion a condition of its metal-roof discount.
So before you pay more for Class 4 to get a credit, ask your own insurer these questions, in writing if you can:
- Do you offer a premium credit for a Class 4 roof on my policy, and what product list or certificate do you accept?
- Does getting the credit require a cosmetic damage exclusion or waiver? Can I read the exact wording first?
- What does that wording do to a future hail claim on this roof?
- If I am replacing the roof after a claim, does my policy pay any part of the difference between a Class 3 and a Class 4 product? That depends on your policy, and your insurer decides.
Our guides on replacement cost and actual cash value and on negotiating a roof insurance claim cover how those terms work.
What to put in the bid
A roofing bid that says “impact-resistant shingles” is not specific enough to compare. Ask every contractor for the same four things, in writing.
- The exact product line. Not “architectural shingle.” Timberline HDZ and Timberline UHDZ are different products with different classes.
- The class, and proof of it. Ask for the Class 4 statement printed on the package, or a copy of the certificate, and keep a photo of the label before it is installed. GAF and State Farm both tie the rating or credit to labeled products.
- The accessories. Ask whether the hip and ridge shingle belongs to the same Class 4 system. Owens Corning says its ProEdge STORM hip and ridge is required to complete its Class 4 roof system.
- The cost difference as its own line. Ask each contractor to price the roof as a Class 3 product and as a Class 4 product, so you see the added cost. Then you can weigh it against whatever your insurer says it offers.
Otter Quotes sends one written scope to multiple contractors, so the bids you compare are for the same work.
Where Otter Quotes fits
Otter Quotes creates a written scope of work for your project and sends it to multiple contractors. Contractors who receive the scope can submit bids on that same scope and the same measurements. You compare the bids online, next to reviews and licensing information, and sign online without a salesperson in your home. Subcontractors bid too, so you may be able to work directly with the crew that does the work. We do not work with your insurance company. We are not a contractor, we do not sell upgrades, and we do not offer inspections or assessments. Contractors pay Otter Quotes a fee on the accepted bid.
Frequently asked questions
What does Class 4 mean on a shingle?
Class 4 is the highest rating under the UL 2218 impact test, where a 2-inch steel ball is dropped from 20 feet and the shingle must not crack, tear or open. It is a lab result for one product. It does not make a roof hail-proof.
Is Timberline HDZ a Class 4 shingle?
No. GAF lists Timberline HDZ as Class 3. GAF lists Timberline UHDZ, when sold in packages bearing the UltraMat logo and Class 4 statement, and Timberline AS II as Class 4.
Does a shingle warranty cover hail damage?
Usually not. GAF, IKO and Owens Corning state that hail damage is not covered under their limited warranties. Read the warranty for the exact product on your bid.
Will my insurer give me a discount for Class 4 shingles?
This guide cannot say. Some insurers offer premium credits for impact-resistant roofs, and amounts vary by company and state. Some tie the credit to a cosmetic damage exclusion or waiver. Ask your own insurer, and read the wording before you agree.
What should I ask a roofing contractor about Class 4 shingles?
Ask for the exact product line, the Class 4 label or certificate for it, whether the hip and ridge shingle is part of the same rated system, and the price difference from a Class 3 option as its own line in the bid.
Does Otter Quotes work with my insurance company?
No. We do not work with your insurance company, we do not offer inspections or assessments, and we are not a contractor. Otter Quotes creates a written scope of work for your project and sends it to multiple contractors, who can submit bids on that same scope. Questions about your policy go to your insurer.
Sources
- UL Solutions, “UL Solutions, IBHS Drive Trust in Residential Roofing Shingles,” September 11, 2023, as read October 19, 2026: four classes by steel-ball drop; breach damage viewed from the back; no account of denting or granule loss.
- IBHS, “Relative Impact Resistance of Asphalt Shingles,” August 2014, as read October 19, 2026: ball sizes by class; no product passed more than Class 2 at every double-impact location; steel balls do not exactly replicate hail; insurer criteria differ.
- GAF, impact-resistant roof page, as read October 19, 2026: Class 3 and Class 4 test descriptions; hail excluded from GAF limited warranties; discounts not guaranteed; cosmetic waiver warning; Class 4 line list.
- GAF, Timberline UHDZ product page, as read October 19, 2026: Class 4 only on packages with the UltraMat logo and Class 4 statement; no hail warranty.
- GAF, Timberline HDZ product page, as read October 19, 2026: Class 3; no hail warranty.
- Owens Corning, TruDefinition Duration STORM page, as read October 19, 2026: UL 2218 Class 4.
- Owens Corning, Duration STORM product literature (PDF), as read October 19, 2026: Class 4; hip and ridge required to complete the Class 4 system; see actual warranty for limitations.
- Owens Corning, Standard Product Limited Lifetime Warranty on Roofing Shingles and Components, Pub. 10023873-I, August 2026, as read October 19, 2026: “Acts of God, such as hail” listed among conditions not covered; Duration STORM named in the warranty tables.
- IKO, Cambridge shingle page, as read October 19, 2026: hail damage not covered under the limited warranty.
- CertainTeed, impact-resistant shingles page, as read October 19, 2026: test heights, pass criteria, Class 4 for its impact-resistant line.
- State Farm, “Roofing: Premium Credits Product Listing,” last revised October 1, 2026, as read October 19, 2026: Indiana among states listed; Class 3 and Class 4 entries; certification label; overlays; metal needs a signed Cosmetic Damage Exclusion.
- State Farm, impact-resistant roofing consumer page, March 27, 2023, as read October 19, 2026: discount names, percentages and eligibility vary by state.
- Texas Department of Insurance, roofing discounts page, as of February 24, 2023, as read October 19, 2026: Class 4 receives the highest credit in Texas; amounts set company by company.