Class A Flame Spread Rating Affect Assembly?

12/7/2022

If a material has a Class A flame spread rating, can I assume that it does not diminish the rating of a fire-rated assembly?

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5 Comments

John A Dalton

12/7/2022 08:12:56 am

No. The fire tests are very different for flame spread and assembly tests. Foamed plastic for instance can have a Class A rating but you wouldn't put it into a fire-rated assembly without some testing. Thanks, John

Alex

12/7/2022 08:17:15 am

Are you asking if a wall with Class A finishes has a fire rating? If so, it may but it will not be treated as a fire rated assembly. Class A finishes include brick, gypsum, and cement exterior finishes.

To achieve a fire rating, the entire assembly will need to be constructed to restrict the spread of fire. Therefore, all openings will need to be protected.

Glenn Berger

12/7/2022 08:25:30 am

If I am reading the question correctly -- You have a fire-rated (wall) assembly and you want to add a finish (partial or full) that has a Class A flame spread rating.

I would say that the fire-rating of the assembly would be not affected with the addition of an interior finish that has a Class A flame spread.

James

11/19/2023 11:45:58 am

Not true, to get a functional rating you MUST test the assembly (if you wish to be accurate) testing the surface only and not the assembly is completely arrant. I can almost guarantee that every assembly behaves quite differently from the surface test. Together is the key to testing.

Todd E Wyatt

12/7/2022 08:53:42 am

The fire-resistance rating (FRR) of a building elements (e.g. primary structure), components (e.g. gypsum board), or assemblies (e.g. shaft walls) are tested per ASTM E119 or UL 263. Per 2021 IBC 703.2.1.4, “Where materials, systems or devices that have not been tested as part of a fire-resistance-rated assembly are incorporated into the building element, component or assembly, sufficient data shall be made available to the building official to show that the required fire-resistance rating is not reduced.”

For instance, a nonbearing 2-Hour FRR partition (tested by UL) such as U411 (https://www.buildsite.com/pdf/ulsystems/Installation-Instructions-2115390.pdf) permits “batts and blankets” (Item 3) as part of this assembly. It also includes (6) alternates to these “batts and blankets”. If you were to include a different insulation material not listed in the listed assembly, you would have to consult with the AHJ that the “required fire-resistance rating (was) not reduced.”

2021 IBC Chapter 8 Interior Finishes “contains the performance requirements for controlling fire growth and smoke propagation within buildings by restricting interior finish and decorative materials. The provisions of this chapter require materials used as interior finishes and decorations to meet certain flame spread index or flame propagation criteria and smoke development criteria based on the relative fire hazard associated with the occupancy. The performance of the material is evaluated based on test standards.”

Depending on the Occupancy Group (e.g. Assembly, Residential, Institutional, etc), if the building is sprinklered or not, and the location (e.g. stairway vs corridors vs rooms) of the Interior Finish (wall & ceiling), the Interior Finishes will have a flame spread index & smoke-developed index of Class A, B, or C. The method of attachment (direct or furred or set-out) of the Interior Finishes onto FRR or noncombustible Building Elements is also prescribed. Chapter 8 also addresses “decorative materials and trim”.

Lastly, Chapter 6 Types of Construction 603.1 Allowable Materials includes a list of “combustible materials … permitted in buildings of Type I or II” (e.g. noncombustible) such as “wood nailers for parapet flashing and roof cants.”

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Class A Flame Spread Rating Affect Assembly?

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