Primary structural member fire protection

[tuzi]

I have a question regarding the fire rating of structural members. This is an A (round level) and R-2(level 2 to 5) building. The parking garage is IA. At the building entrance, the structural design includes columns and W-beams supporting a portion of the floor above an exterior space. The construction type is IIB, which does not require a fire rating for the primary structural frame.


Although a 1-hour floor/ceiling assembly is required to separate dwelling units, in this case, the unit is located above an exterior space. Based on that, it seems like the supporting columns and beams wouldn’t need to be fire-protected. Did I miss anything?

 

[Yankee Chronicler]

Please disregard.

 

[RLGA]

Please disregard.

Why?

 

[Yankee Chronicler]

Why?

Because I posted a response, then I re-read the question and realized that my response had been incorrect. Unfortunately, there's no way to retract a post, so all I could do was to edit it out.

 

[walker.t]

Based on that, it seems like the supporting columns and beams wouldn’t need to be fire-protected.

The fire-resistance rating of building elements in Table 601 is based on the type of construction, dwelling unit separations are not a concern in this regard.

Did I miss anything?

Maybe. You didn’t say which Group A you have, but except for A-5 you can’t get a 5-story building in Type IIB construction, therefore you can’t use nonseparated mixed occupancy and will be using separated occupancies per 508.4. If your exterior space under the R-2 is considered Group A you’ll need to provide an occupancy separation per Table 508.4 which is 1-hour (for a sprinklered building, NFPA 13 sprinklers required for a 5-story R-2.) Per 508.4.4.1, the occupancy separation must be constructed as a fire barrier or horizontal assembly. Per 711.2.1, supporting construction for the horizontal assembly (the floor/ceiling separating the R-2 and the exterior space) needs to be protected to match the rating of the horizontal assembly, therefore your columns will need a 1-hour rating.

You didn’t ask about exterior walls, but make sure your exterior walls don’t need a rating due to fire separation distance per Table 705.5.