Harold:
The condo developement that is on the last bldg (22 units each) has each units feeder run thru the common hallways, and the risers are thru a common chase to the second & third floors.
The feeders thru the common hallways are installed within the truss type floor joists, fire/draft stopped at all penetrations, and then one layer of 5/8 FC shtrk is installed on the bottoms of the joists. Framing is then installed (8" drop) and the sprinkler lines, HVAC and any other items are mounted in this space, and the bottom is rocked w/ 5/8". The common chase mentioned above is 5/8 rock inside & out.
There are no feeders in the truss attics, only required lighting & radon fans.
Now, the 'old' buildings.....that's another story....
