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2nd level subterranean parking garage - tricky exit access question

Yikes

SAWHORSE
Joined
Nov 2, 2009
Messages
4,105
Location
Southern California
See the (roughly drawn) conceptual section / illustration below. My exit analysis is in red, and my code issue / question is in blue.
We have an apartment building design on a very small lot, with 2 levels of subterranean parking. Both parking levels have only 28 occupants.
The lowest level P2 requires min. 2 paths of exit access:
  • one is to a stairwell #A, which eventually exits to grade;
  • the other is to stair #B which simply connects to level P1 (doesn't go up to grade level).
Level P1 (occ load=28) is only one story below grade plane, so it only requires one exit access, which is stair #A.
Exit access paths converge when entering the door at stair #A, but not before that.
Therefore, the occupant load at level P1 is not cumulative, and remains at 28. Level P1 is allowed to have only one exit access, even though it is receiving some occupants form P2 below.
The exit width at stair #A door convergence (CBC 1005.6) is based on the cumulative load of 28+14, but that's solely for purposes of determining exit component width, not for determining occupant load for Table 1006.3.3(2).
Is this correct?



1636142167803.png
 
Last edited:
See the (roughly drawn) conceptual section / illustration below. My exit analysis is in red, and my code issue / question is in blue.
We have an apartment building design on a very small lot, with 2 levels of subterranean parking. Both parking levels have only 28 occupants.
The lowest level P2 requires min. 2 paths of exit access:
  • one is to a stairwell #A, which eventually exits to grade;
  • the other is to stair #B which simply connects to level P1 (doesn't go up to grade level).
Level P1 (occ load=28) is only one story below grade plane, so it only requires one exit access, which is stair #A.
Exit access paths converge when entering the door at stair #A, but not before that.
Therefore, the occupant load at level P1 is not cumulative, and remains at 28. Level P1 is allowed to have only one exit access, even though it is receiving some occupants form P2 below.
The exit width at stair #A door convergence (CBC 1005.6) is based on the cumulative load of 28+14, but that's solely for purposes of determining exit component width, not for determining occupant load for Table 1006.3.3(2).
Is this correct?



View attachment 8335
Interesting scenario here...

I think you will get hung up on the highlighted code section below. Since Level P2 requires two means of egress, you are required to maintain those two means of egress all the way to the exit discharge. Combining the two exit/exit access paths on Level P1 seems to violate this requirement.

1636378257982.png
 
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