My "ceiling joists" are 2x14 steel I-beams. The steel thickness is about 5/16" or so. The room void is 24'x32'. The clearance between the beams and the drywall is planned to be 6" to allow for basement headroom below the drywall and some utility clearance above the drywall (including framing above). I can put 2x4 nailers on the poured concrete perimeter walls, but how do I support a drywall ceiling away from the perimeter walls?
Above the ceiling joists are some 2x12 engineered floor joists for the next level up. I was thinking about possibly hanging some 2x4's from these and using these "inverted columns" to support the drywall framing. I was planning to sandwich the joist webbing with some scrap 2x4 pieces cut to the "width" of the webbing to use to nail the support columns to. If I go this route, I plan to put one 2x4 "drop column" every 8 feet. I think that would be enough structure to support the drywall, but I can put in more if necessary.
I could theoretically drill into the steel I-beams, but I would have no idea how hard this might be, and I would prefer to avoid drilling in to them. The I-beams were an automobile bridge in their previous life.
If someone has an opinion or suggestion that might work, I'm more than willing to listen. I've never had a framing problem like this before. Previously there was a suspended tile ceiling and the support wires were just looped over the beams.