Regarding IBC (2021) 708.4 exceptions #2 and #3:
Exception #2- Seen frequently in dwelling unit/corridor separations, allows fire partitions serving as corridor walls to not extend above the lower membrane of corridor ceiling, if the room side (2.1) membrane of the corridor wall extends to deck of a rated assembly. Protection of ducts/transfer openings and penetrations at the wall line above the corridor lid membrane is inferred since you are crossing into another required separation (unless the exceptions to 717.5.4 apply). Grilles in the lid must be protected per 717.5.4.1 (2) with ceiling radiation dampers.
Exception #3 (Tunnel corridor)- Rating (fire partition) terminates at upper membrane of the corridor ceiling assembly. Infers that rating stops and no other penetrations above this are required to be protected. The lid is required to have a corridor damper per 717.5.4.1 (3).
What if you have a VB non-sprinklered ‘B’ occupancy with a rated corridor due to occupant load and you want to utilize exception #2 above? Does the rating in that instance carry to deck, therefore requiring possible fire dampers for ductwork traversing across the corridor/room wall above the lower membrane of the lid, if you have no rated floor/ceiling assembly? Or does the rating stop at the corridor lid membrane since there is no reason for the wall to continue up for separation, but does anyway? Does this infer that you can only use exception #2 when you have a rated floor/ceiling assembly above the corridor?
The wording “shall not be required to extend above the lower membrane of a corridor ceiling…” for exception #2 and “shall be permitted to terminate at the upper membrane of the corridor ceiling assembly” has me believe that there are differences in the application.
A simpler question perhaps: Is that room side single layer of gyp extending to deck considered a continuation of the fire partition (rating) if the room abutting the corridor is not required to be rated?
Thanks in advance!
Exception #2- Seen frequently in dwelling unit/corridor separations, allows fire partitions serving as corridor walls to not extend above the lower membrane of corridor ceiling, if the room side (2.1) membrane of the corridor wall extends to deck of a rated assembly. Protection of ducts/transfer openings and penetrations at the wall line above the corridor lid membrane is inferred since you are crossing into another required separation (unless the exceptions to 717.5.4 apply). Grilles in the lid must be protected per 717.5.4.1 (2) with ceiling radiation dampers.
Exception #3 (Tunnel corridor)- Rating (fire partition) terminates at upper membrane of the corridor ceiling assembly. Infers that rating stops and no other penetrations above this are required to be protected. The lid is required to have a corridor damper per 717.5.4.1 (3).
What if you have a VB non-sprinklered ‘B’ occupancy with a rated corridor due to occupant load and you want to utilize exception #2 above? Does the rating in that instance carry to deck, therefore requiring possible fire dampers for ductwork traversing across the corridor/room wall above the lower membrane of the lid, if you have no rated floor/ceiling assembly? Or does the rating stop at the corridor lid membrane since there is no reason for the wall to continue up for separation, but does anyway? Does this infer that you can only use exception #2 when you have a rated floor/ceiling assembly above the corridor?
The wording “shall not be required to extend above the lower membrane of a corridor ceiling…” for exception #2 and “shall be permitted to terminate at the upper membrane of the corridor ceiling assembly” has me believe that there are differences in the application.
A simpler question perhaps: Is that room side single layer of gyp extending to deck considered a continuation of the fire partition (rating) if the room abutting the corridor is not required to be rated?
Thanks in advance!