I have a floor opening from the second floor down to the first floor, there is no stair located in the opening, it is just an opening. The floor opening is about 1/4 of the ceiling area in the first floor entrance / exit lobby. The client wants the floor opening open at the second floor so we propose to put the closure fire barrier walls at the first floor.
Do these walls on the first floor have to be located immediately at the edge of the floor opening? Can I use the lobby walls as the enclosure walls? One main point is that there is a 3 story enclosed exit stair that exits into the lobby per section 7.7.2 and traverses the lobby to the exterior exit door and other areas on the first floor that must pass through the lobby to an exit.
I interpret 8.6.8 as to requiring the walls immediately at the floor opening. The illustration in the 101-2012 handbook shows enclosure walls at the first floor immediately at the edge of the floor opening in the second floor.
Any help is much appreciated.