I'm following up here in case anyone is interested in any further info we've acquired. We are doing an appeal / offering life safety equivalencies for the particular project in question as they ultimately wanted to interpret as B occupancy (A-2 less than 50) which would limit to 29 occupants, but we had capacity for 43.
1006.3.2 Single Exits
A single
exit or access to a single
exit shall be permitted from any
story or occupied roof where one of the following conditions exists:
- The occupant load, number of dwelling units and common path of egress travel distance does not exceed the values in Table 1006.3.2(1) or 1006.3.2(2).
- Rooms, areas and spaces complying with Section 1006.2.1 with exits that discharge directly to the exterior at the level of exit discharge, are permitted to have one exit or access to a single exit.
We ended up agreeing with the AHJ that our differences in interpretation came down to this phrase: '
exits that discharge directly to the exterior at the
level of exit discharge'
They interpreted it as meaning only exterior exit doors were permitted; meaning that the occupied space must be at the level of exit discharge and thus an occupied roof would not be acceptable. We challenged that our exterior exit stair was a code defined exit and discharged directly at the exterior at the level of exit discharge as the language does not stipulate that one must enter the exit also at the level of exit discharge.
We ended up reading all the code commentary for 2015 and 2012; frankly it didn't really make anything more clear and there were several errors with references in the 2015 commentary to code sections from 2009-2012 editions that were substantially changed in 2015 so it didn't totally follow. There is a code commentary example of a mezzanine in a tenant suite cited as being compliant per 1006.3.2.2 as well, which was a good case for vertical travel being permissible.
We read through 2009 and 2006 comparable code sections, and found a highly explicit bit of language in 2006 that is much clearer, though they consistently refer to entire buildings rather than just stories or spaces: 2006 IBC 1019.2.3 'Single-level buildings with the occupied space at the level of exit discharge...'(are permitted to have only one exit). We felt it was noteworthy that 'occupied space at the level of exit discharge' was removed from later versions of the code.
Our home jurisdiction uses NFPA 101 in addition to IBC, so we are very familiar with it and with the single exit criteria from upper levels. We referenced some similar past projects that were permitted under our home AHJ and cited NFPA 101 single exit criteria. We found some language in those code sections that is quite similar to IBC and uses the phrase 'exits that discharge directly to the exterior' but gives requirements for stairs- implying that NFPA 101's interpretation of the phrase in 1006.3.2.2 matches ours- meaning that vertical travel within exits is permitted.
NFPA 101 38.2.4.4
Any business occupancy three or fewer stroies in height, and not exceeding an occupant load of 30 people per story, shall be permitted a single separate exit to each story provided that all fo the following criteria are met:
(1) The exit shall discharge directly to the outside.
(2) The total travel distance to the outside of the building shall not exceed 100'.
(3) The exit shall be enclosed in accordance with 7.1.3.2 and both of the following shall also apply:
(a) The stair shall serve as an exit from no other stories
(b) A single outside stair in accordance with 7.2.2 shall be permitted to serve all stories.
