Sifu
SAWHORSE
- Joined
- Sep 3, 2011
- Messages
- 3,391
Given: two story, VB, non-separated, sprinklered multi-tenant building, B, S-1. A single tenant space occupies two floors, it has space has a furnace room with supply and return ducts penetrating the floor of the 2nd level, up to the drop ceiling. See the picture. There is a wall surrounding the ducts on the 2nd level, so the opening is concealed by construction.
The way I understand it, a shaft is an option, but not required per 717.6.3. The other option permitted by this section allows the penetration if surrounded by fire-blocking, with no prohibition on it being concealed by construction. So the end result is supply and return, through the floor, hidden behind a non-rated wall, to the ceiling then branched out above the ceiling, with fire-blocking at the floor level. I think this meets code. IBC 714.6.2 would also appear to allow this, if the annular space is filled with material to resist the free passage of flame and smoke.
Now, say the applicant wants to enclose the ducts with a rated shaft wall. Same exact condition, only now the wall is rated, and eliminate the fire-blocking. That triggers IBC 713, for shafts. This section would require enclosure at the bottom by either fire dampers or room enclosures unless by exceptions, which (both) would prohibit the openings for the branch supplies. It would also require continuity to the underside of the roof deck or a rated lid. Do that, and I think it meets code.
My thinking is that the only way to eliminate the fire-blocking/annular space fill is with a compliant shaft (with top and bottom enclosure). Otherwise, require the fire-blocking and ignore the fact that the wall surrounding the ducts is rated.
Make sense? Or am I way overthinking?
The way I understand it, a shaft is an option, but not required per 717.6.3. The other option permitted by this section allows the penetration if surrounded by fire-blocking, with no prohibition on it being concealed by construction. So the end result is supply and return, through the floor, hidden behind a non-rated wall, to the ceiling then branched out above the ceiling, with fire-blocking at the floor level. I think this meets code. IBC 714.6.2 would also appear to allow this, if the annular space is filled with material to resist the free passage of flame and smoke.
Now, say the applicant wants to enclose the ducts with a rated shaft wall. Same exact condition, only now the wall is rated, and eliminate the fire-blocking. That triggers IBC 713, for shafts. This section would require enclosure at the bottom by either fire dampers or room enclosures unless by exceptions, which (both) would prohibit the openings for the branch supplies. It would also require continuity to the underside of the roof deck or a rated lid. Do that, and I think it meets code.
My thinking is that the only way to eliminate the fire-blocking/annular space fill is with a compliant shaft (with top and bottom enclosure). Otherwise, require the fire-blocking and ignore the fact that the wall surrounding the ducts is rated.
Make sense? Or am I way overthinking?
