UL 2218 Impact · ASTM E108 Fire · Wind Specs (2026)
Class 4 Impact-Resistant Shingles (UL 2218)
An impact resistant roof is sold with one number — Class 4 — and buried under three misconceptions: that it means wind-rated, fire-rated, or insurance-discounted. This guide separates the UL 2218 hail test from the Class A fire rating and the 130 mph wind spec, then runs the math on when Class 4 actually pays.
Hail comes often (hail-alley / Gulf states)
Class 4 is the highest-value upgrade in roofing for you. Pair the shingle with the 6-nail wind spec and file the certification with the carrier the week the roof is done.
Occasional hail (every 5–10 years)
Worth pricing. If your carrier offers a Class 4 premium discount in your state, the material upcharge usually pays back in 1–3 years; without a discount, buy Class 4 for durability, not economics.
Rare hail (coastal, Pacific Northwest)
Skip the Class 4 premium unless the carrier discounts it anyway. Spend the budget on the 130 mph wind system and ventilation instead — wind and moisture, not hail, age your roof.
UL 2218 Impact Classes, One Steel Ball at a Time
The test is almost childishly simple: a steel ball of set diameter drops 20 feet onto a shingle backed by plywood, and inspectors look for cracks on both sides. Only the ball diameter changes between classes — and only Class 4 demands the same spot be hit twice.
| Class | Steel ball drop | Simulated hail | Typical shingle response | Insurance discount band |
|---|---|---|---|---|
| Class 1 | 1.25 in steel ball | Pea to marble (≈ 1.25 in) | Standard 3-tab and architectural shingles pass; cosmetic granule loss still occurs in real hail | Rarely discounted |
| Class 2 | 1.5 in steel ball | Small hail (≈ 1.5 in) | Standard shingles pass with margin; mats may craze under back-side inspection | Occasional small credit |
| Class 3 | 1.75 in steel ball | Moderate hail (quarter-to-golf territory) | SBS-modified and reinforced-mat shingles pass; the class where discounts usually begin | ≈ 5–10% where offered |
| Class 4 | 2.0 in steel ball, twice in the same spot, from 20 ft | Severe hail (larger than a golf ball) | No cracking, tearing, or splitting — SBS rubberized asphalt or reinforced mats absorb the impact | ≈ 10–30% premium discount where the state and carrier offer it |
Certification belongs to the product, not the roof: look for the UL 2218 Class 4 listing on the wrapper or the manufacturer’s certification letter. An installer’s “impact-resistant” verbal claim is not a listing.
💡 Tip: Class 4’s real material magic is SBS — rubberized asphalt that flexes instead of fracturing. The same chemistry improves tear resistance during installation and cold-weather flexibility.
⚠️ Warning: Class 4 is an impact rating, not a wind rating — the two certifications are independent. A Class 4 shingle at a 4-nail pattern still rates its 110 mph base, not 130.
❌ Don’t: assume the discount. It is never automatic — submit the UL certification and invoice to the carrier, and get the credit confirmed in writing before the roof is paid for.
Fire & Wind Ratings Reference — the Other Two Numbers
Roof “classes” collide in search results because three different standards use the word. Class A fire, UL 2218 impact classes, and wind mph each answer a different threat — a roof’s full armor is all three, and none of them implies the others.
| Rating | What it means | Common on |
|---|---|---|
| Class A fire (ASTM E108) | Withstands severe fire exposure — effective flame spread ≤ 25, with burning-brand test. The rating most wildfire-zone codes require. | Most architectural asphalt shingles over proper underlayment; standing-seam metal; most concrete and clay tile |
| Class B fire (ASTM E108) | Moderate fire exposure resistance — flame spread between 26 and 75 territory. | Some treated wood shake and lower-tier assemblies; increasingly rare in new residential work |
| Class C fire (ASTM E108) | Light fire exposure — the minimum most residential codes accept outside wildland zones. | Some aluminum and lightweight assemblies; check the listing, not the category |
| 3-tab wind (ASTM D3161/D7158) | Typical listings run 60–80 mph at the standard 4-nail pattern with sealant intact. | Entry-level 3-tab strips — the first shingles to tab in a storm |
| Architectural wind (D7158 Type H) | 110 mph base at 4 nails; 130 mph only with the full high-wind spec — 6 nails, brand starter, registered system. | Timberline HDZ, Duration, Landmark, Cambridge and peers |
| SBS + 6-nail enhanced spec | Rubberized (SBS-modified) shingle with the 6-nail detail holds the 130 mph enhanced tier with better uplift margin at the tabs. | Class 4 flagship lines and storm-market premium installs |
The “hurricane proof roof” phrase in marketing is not a rating any standard issues — the honest equivalents are the 130 mph enhanced wind system (shingle + 6 nails + starter + registration) and impact Class 4 for the hail component. Wind uplift fails at edges and tabs first; nailing pattern and starter spec do more work than the shingle’s price tier.
How the Insurance Discount Actually Happens
The discount exists because hail claims are the costliest catastrophe line most carriers pay, and a Class 4 roof measurably reduces claim frequency. But the mechanism is paperwork, not telemetry: the carrier does not know your shingle’s rating until you tell it. The working sequence — confirm first, install second, file third — protects the economics from the two classic failures: buying Class 4 in a state where the carrier offers no credit, and installing it then losing the discount to missing documents.
- 01
Call the carrier before ordering. Ask: is a Class 4 (UL 2218) premium credit offered in my state, what is the dollar amount, and what documentation triggers it?
- 02
Buy a listed product. Keep the wrapper and request the manufacturer's UL 2218 Class 4 certification letter for the exact product name on the invoice.
- 03
Install with the full spec. The enhanced wind tier — 6 nails, brand starter, ice-and-water rows — is a separate requirement from the impact listing; do both while the crew is up there.
- 04
File within the policy cycle. Submit the certification letter, the itemized invoice naming the product, and any endorsement forms the carrier requires. Get the credit confirmed in writing.
- 05
Re-file on reroofs. The credit is a property of the current roof; a future standard-shingle replacement silently removes it.
State rules differ — some states restrict how carriers factor roof age and class into pricing, and a few mandate the credit. This page describes the general mechanism; your policy and your state’s insurance department govern.
Class 4 breakeven estimator
0.8 yr
Upcharge $840 ÷ discount $1,000/yr. Pays back inside two years — strong candidate.
Typical inputs: 28 sq reroof, $20–50/sq Class 4 premium, $300–2,000/yr credit where offered.
Impact ratings are bought before the stormPhoto: UnsplashWhich Materials Actually Carry Class 4
Three families dominate the Class 4 listing rolls, each reaching the rating a different way — by flexing, by armoring, or by simply being rigid enough to shrug a steel ball off.
SBS-modified asphalt
Rubberized (styrene-butadiene-styrene) asphalt lets the mat deform and recover — the shingle absorbs the ball instead of resisting it. This is the residential hail-alley favorite: Class 4 at architectural weight, installed by any shingle crew, usually the cheapest impact rating per square. Flagship storm-market lines from all three major brands live here.
Reinforced-mat asphalt
Fiberglass mats with added tensile fabric or polymer grids resist the crack propagation the test scores. A few premium laminates reach Class 4 through reinforcement rather than rubberization, typically at a slightly higher weight and price than SBS lines.
Metal & stone-coated steel
Rigid panels pass easily because they dent rather than crack — and UL 2218 scores cracking and function loss, not cosmetics. A Class 4 metal roof may carry visible hail dents after a storm while keeping its watertight integrity and its insurance listing intact.
Ratings picked? Now size the roof.
Class 4 shingles order by the same wrapper math as any architectural line — roughly 33 ft² per bundle. Get the count from the roof shingle calculator, compare the flagship lines side by side on shingle brands compared, and set expectations for service life with how long shingle roofs last. Every tool lives on the roofing calculators hub.
Class 4 & Rating Questions
What is a Class 4 roof?
Does a Class 4 roof lower my insurance premium?
Is Class 4 shingle worth the extra cost?
What is the difference between Class 4 impact and Class A fire ratings?
Do metal roofs qualify as Class 4 under UL 2218?
What are the most durable roofing materials overall?
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