Just checking, but doesn’t a ceiling between the upper and lower levels of a commercial building need to be drywalled and taped, and anything going through the drywall needs to be sealed with a fire caulk? They had it hidden under a hung ceiling. I just returned from a new 6,000 sq. ft. office building. This city uses 2005 building codes but only code books I own are for older electrical and plumbing. I guess I need to forck out several hundred dollars to buy a complete set. Help!
Dont know about your codes down there, but up here, fire rated drywall is called for as well as fire rated caulking on all protrusions and flow-through’s.
If the building is open to the public like say a golf course clubhouse or a restaurant, then the drywall has to have a 1 hour fire rating, which means double 5/8s drywall.
My last big drywall job was in 2002, a clubhouse for a golf course. The kitchen and all walls abutting it had to be 1 hour rating. The entire basement ceiling, all beams and all columns had to be 1 hour rated. All potlights had to be boxed inside the joist’s with double 5/8s drywall and caulked. Talk about a pain in the shoulders.
Two  layers of 5/8"drywall is rated for 2hrs. The process is one layer taped with the second layer staggered.
Can you be more specific about the building. Is it free standing, sprinklered, wood joists,Firerated T-Bar ceiling,single tenancy etc.
Maybe this will answer some of your questions.