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Cumulative Occupant Loads

VAC

VAC

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Joined
Jul 10, 2022
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Florida's Treasure Coast
Are lobbies and Foyers/Vestibules OL calculated towards the cumulative occupant load when exiting a building?
I am interpreting IBC 2018 1006.2.1 Exception 1 as no, not counted.
But then I read 1004.2 and it sounds like I should, although lobbies are not specifically mentioned here.
I also don't interpret lobbies as intervening spaces. (1004.2.1)

What are your thoughts on this? (and what am I missing?)

Thank you!
 
steveray said:
Total OL...yes...Convergence is addressed in 1005.6ish....A lobby is an intervening space depending on layout...Got a pic?
Click to expand...
I thought of convergence, but my understanding is that 1005.6 applies to the OL of two floors coming together on the level of discharge (where the OL from any space on that level wouldn't be added)

This will be more on the same level, different rooms coming together through a foyer. I don't have a layout yet, as I just started to research the project.

First I looked at 1004.2 - Cumulative Occupant Loads "shall be determined in accordance with this section"...
-Intervening spaces or accessory areas
-Adjacent levels for mezzanines
-Adjacent stores (other than convergence)
I didn't see here anything that was specific, although it says that
"the design occupant load shall be the combined occupant load of interconnected accessory or intervening spaces. Design of egress path capacity shall be based on the cumulative portion of occupant loads of all rooms, areas or spaces to that point along the path of egress travel."
This was a share for this section. I assume the lobby would fall under 'intervening spaces'.
cumulative loads.png

Then I looked at 1006.2.1 specific to egress based on occupant load (and cpotd). So far so good.
Then Exception 1.
The number of exits from foyers, lobbies, vestibules or similar spaces need not be based on cumulative occupant loads for areas discharging through such spaces, but the capacity of the exits from such spaces shall be based on applicable cumulative occupant loads.

This image illustrated that exception in one of the commentary books (International Building code handbook/McGraw Hill-ICC) in the office.
View attachment 20230806_140326.jpg
This is more of the scenario that I'm researching for the project.
Hence my question (and confusion!)

So
Section 1004.2 refers to how to calculate these specific scenarios
-Intervening spaces or accessory areas
-Adjacent levels for mezzanines
-Adjacent stories

Section 1005.6 refers to how to calculate convergence

Section 1006.2.1 refers to the number of exits/capacity.
But what I find contradicting is Exception 1.
It may not be... which is why I think I'm missing (or not accounting for) something.

Is this section treating a foyer for example the same way convergence is treated?
Is it assumed that people in the foyer will exit before everyone else gets there?

Technically the foyer already had an exit, presumably 32" min. so that would take care of that space... then add the load of the additional spaces (although that's not what the second illustration shows, but it's my thought process)
 
180 OL is a 36" clear opening....not a 36" door....The people in the space get added to the egress width but not the number of exits if that makes sense?

VAC said:
The number of exits from foyers, lobbies, vestibules or similar spaces need not be based on cumulative occupant loads for areas discharging through such spaces, but the capacity of the exits from such spaces shall be based on applicable cumulative occupant loads.
Click to expand...
 
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steveray said:
180 OL is a 36" clear opening....not a 36" door....The people in the space get added to the egress width but not the number of exits if that makes sense?
Click to expand...
Yes! always clear opening! and it makes sense. Basically that foyer wouldn't need additional an additional exit, just additional capacity.

So in that second example they don't seem to imply that there was any OL added from the foyer itself, as the 280 is the total of the capacity coming from the other spaces. Yet, no capacity added from the foyer itself... I think?
 
VAC said:
Is it assumed that people in the foyer will exit before everyone else gets there?
Click to expand...

Think movie theater where elderly group of people are waiting to get into a movie and a younger group are exiting after watching a movie. Who will move quicker in an evacuation of the theater? Is it possible the younger group will converge with the older group at the exits at the same time?

2018 IBC
1004.2 Cumulative occupant loads.
Where the path of egress travel includes intervening rooms, areas or spaces, cumulative occupant loads shall be determined in accordance with this section.

1004.2.1 Intervening spaces or accessory areas.
Where occupants egress from one or more rooms, areas or spaces through others, the design occupant load shall be the combined occupant load of interconnected accessory or intervening spaces. Design of egress path capacity shall be based on the cumulative portion of occupant loads of all rooms, areas or spaces to that point along the path of egress travel.
 
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VAC said:
Yes! always clear opening! and it makes sense. Basically that foyer wouldn't need additional an additional exit, just additional capacity.

So in that second example they don't seem to imply that there was any OL added from the foyer itself, as the 280 is the total of the capacity coming from the other spaces. Yet, no capacity added from the foyer itself... I think?
Click to expand...
They added 10+20+150 to get 180?..foyer was 10..?
 
steveray said:
Got it...probably should have something
Click to expand...
right? That's what I'm thinking. Even if the assumption is that there was a door already, whatever capacity they originally calculated should have been included/added to the new capacity based on 1004.2 AND 1006.2.1 .. but

I just found a comment on the IBC commentary for this exception that reads:
If the space is just a passage space, such as a vestibule, this is not considered a situation that is a cumulative occupant load (Exception 1)
Perhaps that explains it?

So... the research continues :)
 
Someone mentioned theatres and I believe that is the only time you might add the theatre ol and the lobby ol, in theatres where the lobby might have the audience for the next show waiting. (Having worked on only performing arts theatres, I've had to sometimes make the case that there will never be an audience in their seats and one waiting in the lobby. An amusement park theatre might, having worked on one Disney venue long ago.)
 
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bill1952 said:
Someone mentioned theatres and I believe that is the only time you might add the theatre ol and the lobby ol, in theatres where the lobby might have the audience for the next show waiting. (Having worked on only performing arts theatres, I've had to sometimes make the case that there will never be an audience in their seats and one waiting in the lobby. An amusement park theatre might, having worked on one Disney venue long ago.)
Click to expand...
A movie theater makes perfect sense, but you are correct, that a performing arts theater is a different scenarios. They don't stagger shows or have them back to back...
 
steveray said:
It really requires a full understanding of the building to decide whether it is "occupied" or not...Sometimes it's just a vestibule/ air break, sometimes it is a place where people congregate...
Click to expand...
That may explain the exception... if it's not considered occupied. Those areas would be included in the gross for the other functions, but they don't really have one other than to let people in and out.
 
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