A rating answers the question its test actually asked.
Fire, wind, and impact classifications
Does a high roofing rating mean my roof is stormproof?
No. A classification describes performance under a named test and its conditions. Fire, wind, and impact tests answer different questions, and the specified assembly can matter as much as the visible covering. Compare the standard, classification, product, and installation together. A rating is neither a guarantee against every event nor a substitute for reading the warranty.
Start with the standard, not the biggest number.Section link
| Claim | What it describes | What it does not establish |
|---|---|---|
| Class A under UL 790 / ASTM E108 | A roof-covering assembly’s response to specified external-fire exposure. | A fireproof building or an interior fire-resistance duration. |
| ASTM D7158 classification | Asphalt-shingle uplift resistance under the method’s conditions. | Performance for every building height, exposure, and installation. |
| UL 580 Class 90 | A classification derived from specified uplift-pressure tests. | A simple promise that the roof survives 90-mile-per-hour winds. |
| UL 2218 impact classification | Response to prescribed steel-ball impacts on prepared roof-covering samples. | Immunity to all hail damage or guaranteed insurance savings. |
Read this table one item at a time
Class A under UL 790 / ASTM E108
- What it describes
- A roof-covering assembly’s response to specified external-fire exposure.
- What it does not establish
- A fireproof building or an interior fire-resistance duration.
ASTM D7158 classification
- What it describes
- Asphalt-shingle uplift resistance under the method’s conditions.
- What it does not establish
- Performance for every building height, exposure, and installation.
UL 580 Class 90
- What it describes
- A classification derived from specified uplift-pressure tests.
- What it does not establish
- A simple promise that the roof survives 90-mile-per-hour winds.
UL 2218 impact classification
- What it describes
- Response to prescribed steel-ball impacts on prepared roof-covering samples.
- What it does not establish
- Immunity to all hail damage or guaranteed insurance savings.
Letters and numbers only have meaning within their own classification system. “Class A” can refer to different subjects in different documents. Write down the test number alongside the class so the proposal’s claim can be checked without guessing.
Fire classification belongs to the specified construction.Section link
UL explains that roof-covering fire tests evaluate exposure originating outside the building. Class A uses severe fire-test exposure, Class B moderate exposure, and Class C light exposure. These are separate from the time-rated fire-resistance assemblies used for other building elements.
Look beyond the covering name to the listed construction. Deck type, underlayment, and other required layers can be part of the classification. If a contractor substitutes one of those components, ask which listed combination the revised proposal follows. A brochure showing a Class A emblem is less useful than the listing that identifies the conditions.
A roof classification also does not settle wildfire exposure around the entire building. Vents, wall intersections, accumulated debris, and nearby combustible materials are different questions. Keep the claim attached to the roof assembly rather than extending it to every route by which a building could ignite.
Wind and hail tests have different limits.Section link
ASTM D7158 assesses sealed asphalt shingles using measured mechanical uplift resistance and calculated wind-induced forces. Its public explanation identifies field sealing influences such as temperature, time, contamination, and interfering fasteners. It also sets conditions for applying the classification. A shingle that performed well in the test still needs the specified installation and suitable project conditions.
UL 580 evaluates assemblies under static and oscillating pressures. The Class 90 label is not a wind-speed warranty. Converting a site’s wind exposure into design pressures involves the building and location; it cannot be done by replacing “Class” with “mph” on a sales sheet.
UL 2218 uses steel-ball impacts. Its scope says that weathering, temperature, and aging effects are not evaluated and that steel-ball results do not directly predict performance under all natural hail conditions. Use it as comparative test evidence. Read cosmetic-damage exclusions and any impact-related warranty terms separately.
Worked example: make two claims comparable.Section link
Proposal A says “Class A, impact resistant, high wind.” Proposal B supplies the exact product, test numbers, classifications, and a listing reference for the proposed deck and underlayment. B provides more checkable information, but it does not automatically identify the better product or installer.
Ask A for the missing references. For both proposals, record the product’s full name, the test edition or listing date, the assembly components, and the attachment details. Then ask who has checked that the stated classification fits the building’s requirements. A different product in the same manufacturer’s family may have a different record.
Next, compare contractual coverage in a separate column. Who pays for a defective product, installation failure, or later repair? What exclusions and documentation apply? Neither a laboratory class nor a manufacturer’s marketing adjective answers those questions.
Finally, retain the final specification and installation records with your warranty documents. If an accessory changes during the work, record the revised assembly rather than keeping an outdated proposal as proof of what was installed. That turns an impressive label into information you can actually use.
Sources and further readingSection link
Understanding Roofing / Updated
Scope and limitations
- Use the current product listing and project requirements to determine suitability; the examples do not select an assembly for a particular building.
Class A, B, and C Roof Ratings
UL Solutions Code Authorities
UL 790 external-fire exposure classes and the importance of the listed roof assembly.
Historical explanatory publication; not used here to establish current local code requirements.
D7158/D7158M-24A: Wind Resistance of Asphalt Shingles
ASTM International
The published scope and significance sections explain sealed-shingle uplift resistance, field sealing influences, and application assumptions.
UL 2218: Impact Resistance of Prepared Roof Covering Materials
UL Standards & Engagement
The public scope describes steel-ball impact testing and explicitly limits correlation with weathered roofs and natural hail.
Certifying Roof Deck Constructions for Wind Resistance
UL Solutions Code Authorities
UL 580 classifications derive from pressure testing, with materials and components specified as an assembly.