Extents for fire protection of structural framing at fire barriers

[chris macko]

Per 707.5.1 (IBC 2021), any structural framing supporting a fire barrier needs to be fire rated to match the rating of the fire barrier. How far past the wall does that need to extend? Say I have a fire barrier running a long a column line, would I just need to protect the steel along that line, or would I need to go 1 bay back from it as well to leave some fire protected steel to support the steel supporting the wall? Logically a single unbraced line of steel doesn't seem to offer much support, but at the same time, if there are no lateral braces in that bay being protected, I'm not sure how much it really helps. I'd love to find some clear code language about this.

 

[steveray]

Per 707.5.1 (IBC 2021), any structural framing supporting a fire barrier needs to be fire rated to match the rating of the fire barrier. How far past the wall does that need to extend? Say I have a fire barrier running a long a column line, would I just need to protect the steel along that line, or would I need to go 1 bay back from it as well to leave some fire protected steel to support the steel supporting the wall? Logically a single unbraced line of steel doesn't seem to offer much support, but at the same time, if there are no lateral braces in that bay being protected, I'm not sure how much it really helps. I'd love to find some clear code language about this.

All the way to the foundation…you need to protect the gravity load path to earth…

 

[chris macko]

Vertically that makes sense, and no confusion there. I'm asking about horizontally. Do we need to rate any adjacent framing to help brace the framing supporting the barrier, or is just the line directly supporting the fire barrier sufficient?

 

[Yankee Chronicler]

Vertically that makes sense, and no confusion there. I'm asking about horizontally. Do we need to rate any adjacent framing to help brace the framing supporting the barrier, or is just the line directly supporting the fire barrier sufficient?

You have to ask the structural engineer. The code requirement for fire barriers is:

707.5.1 Supporting construction. The supporting
construction for a fire barrier shall be protected to afford
the required fire-resistance rating of the fire barrier
supported. Hollow vertical spaces within a fire barrier
shall be fireblocked in accordance with Section 718.2 at
every floor level.

The IBC Commentary for this section adds:

In general, fire barriers must be supported by construction
having an equivalent fire-resistance rating. If
the supporting structure is a primary structural frame
(see the definition in Chapter 2) and supports a fire
barrier wall more than two stories in height, the fireresistance
rating for the supporting structure must be
protected by the individual encasement method in
Section 704.3. If the supporting members are a secondary
structural member, then the supporting structure
can be protected by a membrane as in Section
711 for horizontal assemblies. The intent of this
requirement is to prevent the effectiveness of the
assembly from being circumvented by a fire that
threatens the supporting elements. The requirement
for the supporting construction to be fire-resistance
rated applies to buildings of all types of construction,

This suggests to me that lateral bracing might be "secondary structure," which would require fireproofing. The opposing argument would be that "supporting" means "supporting," not "bracing." So the Commentary could be interpreted to mean that joists as well as beams need to be protected when "supporting" a fire barrier, but that lateral bracing would not because it doesn't "support" the fire barrier.

If your fire barrier is supported on joists (for example), the fire protection would have to include the beams and columns supporting the joists, or the walls supporting the joists. The code doesn't define the word "supporting," so you may need to discuss this question with the AHJ.

 

[chris macko]

ok, so it sounds like if the fire barrier is supported by beams or joists overhead, those beams need to be rated as well as any framing they're supported by, which is also what I was assuming, but there's no real need to rate any framing that may or may not be providing lateral support to that framing. It seems strange to only have a single row of framing rated, but unless there's a lateral brace in the next bay, It's not really provided much in the way of lateral support anyway, aside from some limited moment that the connections would provide.

 

[Yankee Chronicler]

ok, so it sounds like if the fire barrier is supported by beams or joists overhead, those beams need to be rated as well as any framing they're supported by, which is also what I was assuming, but there's no real need to rate any framing that may or may not be providing lateral support to that framing. It seems strange to only have a single row of framing rated, but unless there's a lateral brace in the next bay, It's not really provided much in the way of lateral support anyway, aside from some limited moment that the connections would provide.

It would be "supported" by beams or joists overhead only if it is suspended from them and doesn't bear on the floor below. I think what you are calling "supported by" means "braced by," and this is why I suggested conferring with the structural engineer.

 

[chris macko]

The structural engineer is deferring to me in this case. This is also a rated insulated metal panel wall, so there are intermediate horizontal girts between the columns that the wall is attached to in addition to the attachment at the ground and roof. The UL assembly (U054) specifically says the intermediate girts need to be rated, so that part is clear as well. I'm just trying to figure out if anything beyond that wall is needed. There is a diagonal brace in that wall as well, but it sounds like that does not need to be rated since it's not directly supporting the wall. Nothing is suspended off the framing overhead, it's all sitting on the structure below.

 

[steveray]

The structural engineer is deferring to me in this case. This is also a rated insulated metal panel wall, so there are intermediate horizontal girts between the columns that the wall is attached to in addition to the attachment at the ground and roof. The UL assembly (U054) specifically says the intermediate girts need to be rated, so that part is clear as well. I'm just trying to figure out if anything beyond that wall is needed. There is a diagonal brace in that wall as well, but it sounds like that does not need to be rated since it's not directly supporting the wall. Nothing is suspended off the framing overhead, it's all sitting on the structure below.

I would refer back and let them hang their license on it.....Previously my State has said that it is only gravity loads...But between ICC changes or changes at the State, that may have changed...

 

[Penguin87]

It really depends on what the fire barrier is providing separation against. If say the code requires you to provide a fire barrier around a H-3 room, the fire barrier would generally extend from the floor slab to the roof structure. Since you know the fire is to be protected from the hazardous side of the room, you can even make it a directional fire barrier.

However, I have not ever had a AHJ require me to fire rate the roof structure that the wall is connected to unless there were other code requirements driving that (ie, construction type). Seems like you would risk chasing your tail since you could technically argue that the roof structure is a diaphragm and technically it is all connected and providing lateral support.