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.

 

[steveray]

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.


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.

And that is the real question....What is the "exterior" space used for? It has a roof so it is fire area and is part of the building.......

 

[walker.t]

And that is the real question....What is the "exterior" space used for? It has a roof so it is fire area and is part of the building.......

Reminds me of this thread:

R

Thread 'Building Area vs Fire Area'

Jun 2, 2025

Hello, All. I have a somewhat basic question about the 2021 SC BC.

I am looking for some clarification on the definitions portion of the code.

Area, Building (from the official commentary)...
"Allowable building areas (as established by the provisions
of Chapter 5 and Table 506.2) are a function of
the potential fire hazard and the level of fire endurance
of the building’s structural elements, as established
for the types of construction in Chapter 6. A
building area is the “footprint” of the building; that is,
the area measured within the perimeter formed by the
inside surface of the...

• rosegamble
• Replies: 10
• Forum: Commercial Building Codes

 

[RLGA]

Unless you designed the covered area leading to the entrance to be something more than just a pathway, I would posit that the separation stated in IBC Section 420.3 is not required. Although you must consider the area under the projection of the floor above as part of the building area, which means it must be associated with an occupancy group (likely A, since the OP stated that is the primary occupancy on that floor), the separation per IBC Section 420.3 intends to protect the interior of the building from the spread of fire generated within one dwelling or sleeping unit.

I am getting into semantics here, but Section 420.3 states, "in the same building." Although the covered pathway is within the building area for allowable height and area purposes, it technically is not "in" the building. Thus, in my opinion, the floor structure over the entrance pathway only needs to conform to the requirements of Type IIB construction.

 

[steveray]

Unless you designed the covered area leading to the entrance to be something more than just a pathway, I would posit that the separation stated in IBC Section 420.3 is not required. Although you must consider the area under the projection of the floor above as part of the building area, which means it must be associated with an occupancy group (likely A, since the OP stated that is the primary occupancy on that floor), the separation per IBC Section 420.3 intends to protect the interior of the building from the spread of fire generated within one dwelling or sleeping unit.

I am getting into semantics here, but Section 420.3 states, "in the same building." Although the covered pathway is within the building area for allowable height and area purposes, it technically is not "in" the building. Thus, in my opinion, the floor structure over the entrance pathway only needs to conform to the requirements of Type IIB construction.

I like it....I don't agree fully on intent, but that is OK..I might agree if it is just a walkway with no use/occupancy, but if it is truly an A use space, no bueno.....And then we are back to separated or non-sep and what that looks like...?

But if it is a walkway, is it a corridor?

 

[RLGA]

I like it....I don't agree fully on intent, but that is OK..I might agree if it is just a walkway with no use/occupancy, but if it is truly an A use space, no bueno.....And then we are back to separated or non-sep and what that looks like...?

But if it is a walkway, is it a corridor?

Occupancy separation is a distinct issue from dwelling or sleeping unit separation. Even then, it could be permitted as non-separated occupancies if the allowable height and area work out.

If it is more than just a walkway (e.g., a patio with seating), then dwelling unit separation could be an issue. I have seen entrances like this with landscaping along the sides and/or water features that would make it wider than the pathway, but you could not use it for anything other than a walkway. As for a corridor, it depends on whether it meets the criteria for an exit discharge. A corridor is part of the exit access, so if the entrance doors serve as an exit, and the covered area meets the criteria for an exit discharge per Sections 1028, including the prevention of accumulating smoke and toxic gases per Section 1028.4, then you cannot consider it a corridor.

As for this project, it is hard to say with only the one view provided, but I would be inclined to agree that the exit and exit discharge does not happen until the occupants are out from under the second story cover, because the ceiling is too low with a slight barrier at the edge that could retain smoke. If I were the building official, and they wanted this area not to be a corridor, then they would have to show that smoke and toxic gases would readily dissipate, either through computer modeling or some other acceptable method. The code does not require the complete removal of smoke and toxic gases (it states "minimize the accumulation"), so if the design team can demonstrate that smoke and toxic gases will not create a layer that is lower than normal head height, then that would be acceptable in my opinion.

 

[Yankee Chronicler]

Basic legal principles call for interpreting statutory language (which building codes essentially are -- they aren't statutes, but they are laws adopted pursuant to statutes) according to the plain meaning of the words. Where a provision of the code calls for a fire separation "between" dwelling units, if one of two spaces being separated by a floor-ceiling assembly isn't part of a dwelling unit -- IMHO that section of the code doesn't apply.

 

[steveray]

Basic legal principles call for interpreting statutory language (which building codes essentially are -- they aren't statutes, but they are laws adopted pursuant to statutes) according to the plain meaning of the words. Where a provision of the code calls for a fire separation "between" dwelling units, if one of two spaces being separated by a floor-ceiling assembly isn't part of a dwelling unit -- IMHO that section of the code doesn't apply.

Correct but....

420.3​

Floor assemblies separating dwelling units in the same buildings, floor assemblies separating sleeping units in the same building and floor assemblies separating dwelling or sleeping units from other occupancies contiguous to them in the same building shall be constructed as horizontal assemblies in accordance with Section 711.

If there is an occupancy "under the building" it is in the building IMO....By definition of building area and fire area if nothing else...

[BG]AREA, BUILDING. The area included within surrounding exterior walls, or exterior walls and fire walls, exclusive of vent shafts and courts. Areas of the building not provided with surrounding walls shall be included in the building area if such areas are included within the horizontal projection of the roof or floor above.
[BF]FIRE AREA. The aggregate floor area enclosed and bounded by fire walls, fire barriers, exterior walls or horizontal assemblies of a building. Areas of the building not provided with surrounding walls shall be included in the fire area if such areas are included within the horizontal projection of the roof or floor next above.

 

[Yankee Chronicler]

^^^
Good point