Fire Walls vs. Horizontal Exits

[RBK]

I'm a sprinkler guy, and I design systems for a lot of large apartment buildings. It seems to be pretty common practice to divide the structure up into several "buildings" using fire walls. It has always been my understanding that these fire walls, while creating separate buildings for the purpose of calculating allowable areas, are not considered separate buildings for exiting. It has also been my understanding that a horizontal exit is only created when the distance between stairs exceeds the allowable, regardless of how many fire walls you may pass through.

However, I have recently come accross several architects and building officials that are treating every fire wall as a horizontal exit. The reason given is that every "building" needs two exits, and if it's not a stair it must be a horizontal exit.

I'm not well versed in the building code, so which interpretation is correct? I am currently working under the 2007 CBC, but any answers from those knowledgable about the 2006 or 2009 IBC would be appreciated. I assume the CBC and IBC treat the issue similarly, but I may be wrong.

 

[mtlogcabin]

while creating separate buildings for the purpose of calculating allowable areas, are not considered separate buildings for exiting

You are correct. Look at the definitions of and how a "fire partition" "fire barrier" and "fire wall" are constructed. Basically you are not using a "Fire Wall" to devided the building you are using a "Fire Barrier" the old area seperation wall in the UBC.

 

[cda]

Would have to see a typical floor plan to give you a better answer

Sounds like maybe a mix of terms and maybe not an understanding of the code by a few people

 

[TJacobs]

If you have a true firewall you are creating separate buildings. Not more than one half of your exits can exit through a separate building using a horizontal exit. You can also create a horizontal exit with a fire barrier, but you are not creating separate buildings.

http://www.specsandcodes.com/Articles/The%20Code%20Corner%20No.%2024%20-%20Horizontal%20Exits.pdf

 

[High Desert]

As TJacobs inferred, you can createa horizontal exit with either a "firewall" of "fire barrier" as the definition of "Horizontal Exit" implies. First underlined sentence would be with a firewall and the second would be with a fire barrier. A firewall would create separate buildings but a fire barrier would not. You can use a firewall for both allowable area and a horizontal exit provided it is designed to meet the provisions of both.

EXIT, HORIZONTAL. A path of egress travel from one

building to an area in another building on approximately the

same level, or a path of egress travel through or around a wall or

partition to an area on approximately the same level in the same

building, which affords safety from fire and smoke from the

area of incidence and areas communicating therewith.

 

[AegisFPE]

so which interpretation is correct?

This is an example of where there may be multiple interpretations. When a building gets chopped-up by firewalls, such an interpretation can come into play. One strict interpretation I heard of found that where the firewall crossed a tenant door to the corridor, that the subject tenant space located above the first floor now had only one exit from the building, and was therefore prohibited.I would offer that the IBC code does not necessarily mandate multiple exits per "building." Section 1021.1 requires "all spaces within each story shall have access to the minimum number of approved independent exits..."

Admittedly, the definition in 202 of a "story" begins, "That portion of a building..." However, I would submit that 1021.1 does not require each story to be provided with the minimum number of exits, just access to such exits. Thus, it does not appear that an opening through a fire wall necessarily be an "exit."

Therefore, the IBC could be interpreted to provide for a story in one building to egress through a story in another building. So, just because you see a firewall on the plans, does not mean your design/estimate should necessarily include standpipe hose connections at openings through the wall, because a firewall is not necessarily a horizontal exit... in my interpretation!

 

[cda]

think that is why a plan needs to be seen before a solid answer can be given

 

[Builder Bob]

A fire wall can be a horizontal exit, A fire barrier can be a horizontal exit. Do not get confused with the term exits and fire wall/barrier. They are two (actually three) different things in the code. Chapter 10 which governs exits does not give a prescriptive requirement for how fire barriers and/or fire walls are to be constructed. Nor does Chapter 7 provide details for how a horizontal exit is to be designed for egress purposes.

A designer has many options, therefore as the sprinkler contractor, you would need to coordinate your questions with the design professional of record for the project. The designer may have incorporated some design features that are clear as mud unless you talk directly to the designer. The codes are very open to interpretations all our answers could create more problems than doing face time with the AHJ, Designer, and yourself.

 

[RBK]

I haven't used attachments before, so I hope this comes through for you guys. This a pretty big building, so there are quite a few fire walls. The ones that concern me the most are the one between units 275/276 and the one betweens units 278/280. These are only 75 ft apart. The architect's explanation of the fire walls is that they all occur as horizontal exits, because they are serving as the second exit for a building, at least in one direction. There are some "buildings" with more than two "exits", but even those fire walls that may not be required exits for that "building", may be required for the adjacent "building".Aegis,Your explanation is in aggreement with what I have always thought was the reasoning in the code, though I lack the experience to point out the specific sections. Though, on further review of the standpipe requirements, I am starting to question that reasoning a little. It seems that the ICC has taken the Class I standpipe requirements from NFPA 14, but with the addition of the exception to item 2. They allow standpipes to be omitted at horizontal exits where they fall within 130 ft. of a stair. Is the reason for this exception that they want to treat all such fire walls as horizontal exits, but realize that requiring standpipes at EVERY horizontal exit is overkill if you already have a connection in a nearby stair?

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[TJacobs]

This is an example of where there may be multiple interpretations. When a building gets chopped-up by firewalls, such an interpretation can come into play. One strict interpretation I heard of found that where the firewall crossed a tenant door to the corridor, that the subject tenant space located above the first floor now had only one exit from the building, and was therefore prohibited.I would offer that the IBC code does not necessarily mandate multiple exits per "building." Section 1021.1 requires "all spaces within each story shall have access to the minimum number of approved independent exits..."

Admittedly, the definition in 202 of a "story" begins, "That portion of a building..." However, I would submit that 1021.1 does not require each story to be provided with the minimum number of exits, just access to such exits. Thus, it does not appear that an opening through a fire wall necessarily be an "exit."

Therefore, the IBC could be interpreted to provide for a story in one building to egress through a story in another building. So, just because you see a firewall on the plans, does not mean your design/estimate should necessarily include standpipe hose connections at openings through the wall, because a firewall is not necessarily a horizontal exit... in my interpretation!

The IBC does mandate a minimum of 2 exits per space in 1015.1 and per room or space in each story/building in 1019.1. Table 1015.1 and 1019.2 tell you where 1 exit is sufficient.

 

[TJacobs]

It might also help to have a conversation with the FD to see their viewpoint on where they would expect hose connections to be since they will be the ones using them.

 

[RBK]

The fire department will definately be brought in on this issue. Fortunately, this particular city is very easy to work with and I have a good relationship with the fire marshal. This post was more for my own knowledge. I have always seen fire walls in buildings (though they were previously called area separation walls), but treating them as horizontal exits is a relatively new concept to me.