UL 790 and ASTM E108 are two widely recognized standards used to evaluate the fire performance of roof coverings exposed to fire from outside a building. If you are comparing roofing systems, especially in Florida, it is important to understand that these standards are very closely related and are generally considered equivalent test methods for exterior fire exposure. The main difference is the organization that publishes the standard and how the test results may be used for product certification and code compliance.
What Is UL 790?
UL 790, Standard Test Methods for Fire Tests of Roof Coverings, is a standard published by Underwriters Laboratories (UL). It evaluates how a roofing material or roof assembly performs when exposed to simulated exterior fire conditions.
UL 790 evaluates characteristics such as flame spread, fire penetration through the roof covering, and the potential for burning brands or embers to be generated. The standard establishes three primary exterior fire classifications:
- Class A: Provides a high degree of fire protection against severe fire exposure.
- Class B: Provides a moderate degree of fire protection against moderate fire exposure.
- Class C: Provides a lower level of protection against light fire exposure.
The appropriate classification depends on the roof assembly, its materials, installation method, deck construction, and the testing conditions.
What Is ASTM E108?
ASTM E108, Standard Test Methods for Fire Tests of Roof Coverings, is published by ASTM International. The current active edition is ASTM E108-25. It covers exterior fire exposure testing of roof coverings installed over combustible or noncombustible roof decks.
ASTM E108 includes several test procedures, including intermittent flame exposure, spread of flame, burning brand, flying brand, and, where applicable, rain testing. It also establishes Class A, Class B, and Class C exterior fire exposure classifications.
So, What Is the Actual Difference?
For most roofing professionals and building owners, the most important point is that UL 790 and ASTM E108 address essentially the same type of exterior roof-covering fire performance. UL itself has described UL 790 and ASTM E108 together as the standards covering fire resistance performance of roof coverings exposed to simulated exterior fire sources.
The primary distinction is who publishes and administers the standard:
| UL 790 | ASTM E108 |
|---|---|
| Published by Underwriters Laboratories | Published by ASTM International |
| Used extensively in UL testing and certification programs | Used extensively as an ASTM test standard |
| Evaluates exterior fire performance of roof coverings | Evaluates exterior fire performance of roof coverings |
| Provides Class A, B, and C classifications | Provides Class A, B, and C classifications |
In other words, seeing UL 790 versus ASTM E108 on roofing documentation does not necessarily mean that one roof has substantially different fire-testing requirements from the other.
Why Does This Matter for Florida Roofing?
When selecting a roofing system, do not look only at the name of the test standard. The complete tested roof assembly matters. The deck type, insulation, membrane or shingles, underlayment, attachment method, slope, and installation configuration can all affect the tested fire classification.
A roofing membrane that has achieved a Class A rating in one specific assembly should not automatically be assumed to have the same rating when installed with different components or in a different configuration.
ASTM E108 explains that its tests are designed to provide a basis for comparing roof coverings under controlled exterior fire exposures; they do not represent every possible real-world fire condition.
Bottom Line
UL 790 and ASTM E108 are closely aligned standards for testing the exterior fire performance of roof coverings. The biggest difference is the standards organization behind each designation rather than a fundamentally different purpose. Both evaluate exterior fire exposure and use Class A, B, and C classifications.
For a commercial or residential roofing project in Florida, verify the specific tested assembly and required fire classification, rather than relying solely on a UL 790 or ASTM E108 reference. A qualified Florida roofing contractor can help determine whether the proposed roof system meets the applicable building-code and project requirements.
Related Questions
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