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1021.2 Exception 7 IBC-2012

S

sergoodo

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Oct 27, 2009
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306
2 story building, 1st level tenant spaces require 1 exit for 30 occupants total, All tenant spaces have exit access doors to lobby with exit door at level of exit discharge The tenants on the 2nd level require 2 exits, so the ones coming down the main lobby stairs increase the lobby area occupancy x21

Fiddy occupants in the Lobby
Does the lobby require 2 exit doors? Not according to 1021.2 exception 7, The 1st level lobby is serving the 2nd level and these 3 conditions are met.
1. # exits from story is met
2. Each space complies with 1015.1
3. 2 exits @ 2nd level
 
"Fiddy"?

If the occupants on the first story are not required to egress through the lobby, then they need not be included in the occupant load egressing through the lobby. However, you have to consider the number of occupants assigned to the lobby.
 
Thanks RLGA
1st story occupants have exit access to lobby, so the cumulative load is 51. What are "assigned" occupants? A 500 sf lobby with door at the exit discharge EATD is 20' CPET is zero. Seems I am missing something interpreting 2nd exit access door is required.
 
sergoodo said:
Thanks RLGA
1st story occupants have exit access to lobby, so the cumulative load is 51. What are "assigned" occupants? A 500 sf lobby with door at the exit discharge EATD is 20' CPET is zero. Seems I am missing something interpreting 2nd exit access door is required.
Click to expand...
They may have access to the lobby, but if they have a separate exit that is direct to the exterior and they only require one exit from the tenant spaces, then they are not required to egress through the lobby. The lobby also has an occupant load based on its floor area and the applicable occupant load factor.

What Exception 7 to Section 1021.1 is saying is that if a space on an upper story has its own exits complying with Chapter 10, the exits do not need to be accessed by other spaces on the same story provided the other spaces have access to other exits.
 
RLGA said:
What Exception 7 to Section 1021.1 is saying is that if a space on an upper story has its own exits complying with Chapter 10, the exits do not need to be accessed by other spaces on the same story provided the other spaces have access to other exits.
Click to expand...

Each 1st level Tenant only has Lobby exit, no other exit (30), 2nd level tenant has (21) utilizing the lobby. The lobby is ~500sf (5). Cumulative total is now 56 occupants at the lobby.

Are 2 exits required from lobby? Wait, just had the thought, what about the interpretation that this is actually an interior exit stairway, The exit is about 7' in front of the last riser to the door, no occupancy issue.

If 2nd exit needed to comply, best solution now is start punching out additional door for 1st level tenants reduce occupant load.
 
RLGA said:
What Exception 7 to Section 1021.1 is saying is that if a space on an upper story has its own exits complying with Chapter 10, the exits do not need to be accessed by other spaces on the same story provided the other spaces have access to other exits.
Click to expand...

2 exits are required, not understanding how you can have 1 exit using exception # 7. Using the scenario above as an exception for 2 exits required on the story, results in having 2 exits, actually 3.

On another note, determined the lobby is actually an interior access stairway & elevator lobby
 
I thought the only time occupant loads from different levels had to be added is if they were converging from below and above. The theory is that by the time occupants from an upper level get to the level in question that all occupants on that level will have exited.
 
Ahh, Thanks Paul, just glossed over 2015IBC 1004.1.3 adjacent stories. otherwise a lot of ground floor stair landings would have 2 exits
 
Paul Sweet said:
I thought the only time occupant loads from different levels had to be added is if they were converging from below and above. The theory is that by the time occupants from an upper level get to the level in question that all occupants on that level will have exited.
Click to expand...

Is 2015IBC 1004.1.3 adjacent stories a clarification of 2012 IBC? Does 2012 IBC require an additional exit for >49 cumulative occupants at ground floor landing (room or space) with exit directly to exterior?
 
Didn't we just cover 'egress convergence' in another thread a week or two ago?
Occupants on the level of discharge are not going to stand around and wait for the folks on the second floor to get down the stairs before they leave. So no need to combine them.
 
JBI,
I so totally agree and 2015 clarifies nicely. Without the benefit of 2015 IBC looks like the occupants need to be combined according to 2012 IBC...looking for enlightenment to connect the dots with 2012 code reference.
 
JBI, Quote below from other thread is perfect, looking for location where this logic is codified in the 2012 IBC

I think part of the logic for not combining the occupants from different stories is that most or all of the first floor occupants will be out before the second floor occupants get down the stairs. Since they will not necessarily need the door at the same time, so no need to combine them.
Click to expand...
 
RGLA

Read through this article see if it answers your question


freeway analogy also applies to stairways...even more so. There are two locations in the IBC that touch on this matter. The first location is Section 1003.6, which states, “The required capacity of a means of egress system shall not be diminished along the path of egress travel.” The second location is Section 1004.4, and it states:

Where exits serve more than one floor, only the occupant load of each floor considered individually shall be used in computing the required capacity of the exits at that floor, provided that the exit capacity shall not decrease in the direction of egress travel.


http://www.specsandcodes.com/articles/code_corner/The Code Corner No. 22 - Egress Width.pdf
 
Yes CDA, if I can get an agreement on this "diminish" thing. IF enlightened why equal meaning is assigned to 1004.4 & 1003.6 Then I could resolve example scenario for
2012 IBC
1st floor: (1) lobby door exit/exit discharge
2nd floor: (1) exterior exit stair & (1) open interior exit access stair - to lobby.
-------------------1st floor single lobby exit sized for 30 occupant capacity per 1015.1 & 1021.2
-------------------2nd floor open exit access stair sized for 21 occupant capacity 1005.3.1

....additional stair capacity and/or 2nd lobby exit is not required because:
A.) Adding both, totaling: 51 exit/discharge capacity is >, therefore the required capacity of 30 for the lobby exit and 21 for the access stair are not diminished.
OR?
B.) Adding both, totaling: 51 exit/discharge capacity would create diminished capacities of 30 for lobby exit & a diminished stair capacity of 21.

1004.4 jives with freeway analogy, but the freeway disappears in 2012 however stairway is resolved per 1005.3.1. That leaves an additional lobby door requirement hinging on 1003.6 wait...think I just had a moment
OR?
C.)The lobby exit is sized at 30 and 1003.6 says that the 21 occ heading down the stairs also hit that exit sized at 30...the exit is good, not a diminished capacity for the 21 occ. NO 2nd lobby door required. Of course, if, 31 were headed down the stairs - no bueno.

Quit shaking your heads...could of deleted everything except "C", but I am not (for now). Yes RLGA, I overthinkded the freeway analogy... I am leaving for your enjoyment of some overthink humor. I think? Affirmation would be nice. Thanks all for the input, time spent on responses.



2012 IBC
1003.6 Means of egress continuity.
The path of egress travel along a means of egress shall not be interrupted by any building element other than a means of egress component as specified in this chapter. Obstructions shall not be placed in the required width of a means of egress except projections permitted by this chapter. The required capacity of a means of egress system shall not be diminished along the path of egress travel.
1005.3.1 Stairways.
The capacity, in inches, of means of egress stairways shall be calculated by multiplying the occupant load served by such stairway by a means of egress capacity factor of 0.3 inch per occupant. Where stairways serve more than one story, only the occupant load of each story considered individually shall be used in calculating the required capacity of the stairways serving that story.
 
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