Occupant load distribution and intervening spaces?

[Sifu]

Pretty convoluted plan. Group E, type IIB, sprinklered/voice alarm, 2021 IBC:
Two classroom spaces, one has an OL of 106, the other each with an OL of 123. Each classroom has an exit to the exterior, and a door to the interior of the building. Two exits required from each. However, the door to the interior from each classroom egresses into and through a storage/locker area for band equipment, calculated at 2 occupants, which in turn has a single door that egresses to the corridor via a ramp in one direction and short stair in the other.

1) The door from the storage/locker room to the ramp/stair would have a calculated OL 114. Does this locker area require 2 exits? IBC 1006.2.1 excepts foyers, lobbies, vestibules and similar spaces, but not specifically storage/locker areas. I would like to use it, but not sure I can.

2) The egress plan accounts for all occupants from each classroom at the exterior exit door only, and does not include them at the exit door to the storage/locker area (so the design justifies the single exit door noted in question #1). This reduction in the OL carries throughout the MOE sizing all the way to the exits. The result is a MOE sizing strategy based on herding certain numbers of occupants a certain way, which results in some doors with less capacity than would otherwise be required. This is somewhat understandable given that, for example, if a fire alarm activates while students are in class, and it is reasonable to expect the classroom occupants to go directly outside. It is not understandable if the fire alarm activates after the classroom is dismissed while everyone is entering and occupying the storage/locker area and the rest of the interior MOE. So using 1004.2.1 would I require the egress capacity to include the OL from all rooms along the path of egress, even the rooms that have the direct exterior exit? Unless someone can set me straight I am of the mind that the they OL can't be herded to a single exit based on 1005.5, but it seems like there may be a classroom exception somewhere but I can't find it. This

Posting a small snippet of one of the areas in question. It is full of my marks so it may be confusing. The blue numbers indicate a quick calculation of what I think the OL should be, the red X indicates where they use a number I don't agree with.

 

[RLGA]

Section 1005.5 requires that when two or more exits or access to exits are required, the loss of any single exit or access to an exit must not reduce the capacity or width by more than 50%. This is why you try to distribute the occupant load among all the available means of egress to ensure compliance with this section.

Yes, they can exit 100% of the occupants out through the exterior exit door, but they must be able to show that the means of egress for the other pathway provides for at least 50% of the occupant load, which is nearly impossible (in my opinion) to demonstrate without creating confusion.

As for egress through the locker area, I think this could be better. I do not believe it qualifies as a foyer or lobby by common definition. The closest of the three would be vestibule, but the common definition states it is "a passage, hall, or room between the outer door and the interior of a building: LOBBY." Thus, what all three have in common is that they are spaces between an exterior door and the interior of the building. Therefore, relying on the "or similar spaces" part of the exception would mean it should be an interstitial space between the exterior and the inner part of a building. In my opinion, the storage/locker space does not meet those criteria.

However, to look at it from a different perspective, many office buildings have interior lobbies within office suites, so being immediately adjacent to an exterior door is only sometimes the situation. These interior lobbies are likely afforded the same consideration for the code exception; thus, the storage/locker could be considered a vestibule. A vestibule is definitely not a lobby or foyer, which are more formal spaces that serve a specific use and may have other elements within the space, such as seating, displays, etc. However, a vestibule is (again, this is my opinion) an informal transition space that is strictly for circulation--no other functions should exist in a vestibule.

This condition would be a non-issue if they removed the door at the top landing of the stairs/ramp. If they are concerned about securing what is in the lockers, then move that door opening down to where the lockers are located--problem solved!

 

[Sifu]

This condition would be a non-issue if they removed the door at the top landing of the stairs/ramp. If they are concerned about securing what is in the lockers, then move that door opening down to where the lockers are located--problem solved!

There a a few classroom spaces where they are herding all the occupant's out the exterior door and not contributing to the interior path of egress. The result are a few doors that are undersized, which I don't think is a big hurdle. The storage/locker area seemed to present a bigger challenge.....until you offered the alternatives, both of which I will try to artfully suggest if they object.

I do think the lobby/vestibule exception is intended for spaces where the exit path is directly adjacent to the exit doors as well, though I have seen it for interior spaces such as what you mention. In this case, it seems to be stretched a little too far.

I think they may be doing this for reasons related to the noise from the band rooms so they want an additional wall and door, but I don't think the noise overrides the safety issue.

 

[bill1952]

I agree with Ron's removal of the door at landing but it does defeat the sound lock function or dual use of storage. Though since instrument storage is sometimes in corridors - like lockers - not sure there isn't some justification.

and it is reasonable to expect the classroom occupants to go directly outside

I'd disagree with this if the doors to the exterior are not also the primary entrance. People tend strongly to egress in an emergency the way they entered, regardless of the rational. I've seen the research reports. We don't like to go in an unfamiliar direction to avoid hazards, even if it means initially moving toward the hazard. Great justification for the main entrance to be oversized.

 

[Sifu]

You are correct, I have read the same studies, and turned down my share of exit strategies that tried this. What I wasn't sure of was a classroom exception, but I still can't find it. I may be mis-remembering some other classroom exit exceptions and misplacing them here. I will make my comments and see what shakes out.

 

[bill1952]

The door to exterior was a popular trend when I first got involved with code development - then NFPA combined Assembly and Educational committee 1987. Codes may have favored it a little with reduced width on interior m.o.e. At least that is my recollection. Not sure if they do now. Seemed to be a Florida and south east thing.

 

[steveray]

1. Yes....needs 2 doors.....1006.2.1 cummulative...but you are dumping 100+ people in that room....And it can't be lockable...