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Do you count corridors in occupant load calculations

J

jcaperton

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Joined
Jan 18, 2022
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2
Location
Tampa
I have always included the egress corridors in my occupant load calculation, especially in a business occupancy. I am looking at a floor that has multiple uses (all Healthcare occupancy building) and am trying to determine the actual occupant load for the floor. The uses on the floor are: Assembly unconcentrated, business and mechanical. I have two egress corridors to provide exit access to remote egress stairs. The question is, do we include the exit access corridors as part of the floor occupant load and do I define the use of the corridors as business?
 
It depends:
  • If the occupant load factor is a "net" factor, then, no, you do not include corridors--or any other area not directly within the space.
  • If the occupant load factor is a "gross" factor, then, yes, corridors and any other spaces (e.g., restrooms, small closets, corridors, etc.) to the space in question are included in the gross area.
The next question people tend to ask is, "But what if a story includes spaces with both gross and net occupant load factors that use the corridors?" That is a good question for which the IBC does not have an answer. Here is how I handle it and it has never been a problem for me in the past.
  • If the occupant loads for the story are predominantly based on "net" factors, then I exclude corridors, restrooms, small closets, etc., even though there may be some spaces based on "gross" occupant load factors. However, if a branch corridor only serves a space based on a "gross" occupant load, then I would include that corridor with the gross area. For example, I work on many higher education projects. On one project there were multiple large classrooms (over 1,000 sq. ft. net each) with a large corridor connecting all of them. However, in one area there was a small administration area with offices, a workroom, and a small conference room--this admin area had a small corridor off the larger corridor that connected all of these admin spaces. I excluded the large corridor from any occupant load factor; however, I included the small admin corridor in the gross "business areas" occupant load factor.
  • If the occupant loads for the story are predominantly based on "gross" occupant load factors, then I include them in the gross floor area for the predominant occupant load, unless a corridor exclusively serves an area based on a different gross occupant load factor. Spaces with "net" occupant load factors have the load factors applied only to the net areas of those spaces. If there is a corridor that exclusively serves a space with a "net" occupant load factor, then I exclude that corridor.
 
I think you hit on my predicament. I have both. The assembly portion is NET and the other portions are GROSS which led to the question. It can be argued that the corridors will not be typically occupied as the majority of the area is Assembly and Mechanical, but the building is Healthcare (I-2 in the Building Code). Part of me is wanting to be safe and count the corridor area and part of me is saying it does not count.
 
jcaperton said:
I think you hit on my predicament. I have both. The assembly portion is NET and the other portions are GROSS which led to the question. It can be argued that the corridors will not be typically occupied as the majority of the area is Assembly and Mechanical, but the building is Healthcare (I-2 in the Building Code). Part of me is wanting to be safe and count the corridor area and part of me is saying it does not count.
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Then I suggest using the method I use described in the first bullet.
 
If it is feasible to design for the higher number then do so....Never wrong, just might cost a little more. If you cross some kind of big threshold number, then you can decide to VE it with a lower OL...
 
steveray said:
If it is feasible to design for the higher number then do so....Never wrong, just might cost a little more. If you cross some kind of big threshold number, then you can decide to VE it with a lower OL...
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For egress, that may be possible with little effect on egress width; however, the impact on plumbing fixture numbers might be excessive.
 
RLGA said:
For egress, that may be possible with little effect on egress width; however, the impact on plumbing fixture numbers might be excessive.
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Correct of course....but going with the stricter number may help with future remodel/ change of use concerns that may come up down the road...Kind of like when we suggest that the do the entirety of the health care space with health care wiring....Next year when they convert that storage room or office to an exam room, they will be ripping it all apart for the right wiring.....
 
On a similar note, may you deduct manuvering space at room egress doors from the gross sq. ftg. of assembly rooms?
 
ADAguy said:
On a similar note, may you deduct manuvering space at room egress doors from the gross sq. ftg. of assembly rooms?
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I tried that once--the response from the B.O.: No.

That was only one jurisdiction (cannot recall which one), but I only did it because the occupant load was right at 50 and the space was required to be classified as a Group A-3, a situation that my client wanted to avoid.
 
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