I have a condo sitting on top of a parking garage. All existing framing is cast-in-place and conventionally reinforced with no additional protection (Type I-B construction).

We are doing major rehabilitation (transfer slab repairs, column wrapping, new shear walls, underpinning, etc.)...it is a mess, but interesting.

We have (1) one new column to install to mitigate dead load going into the under-designed existing transfer slab. The column has to start out as being structural steel, because we need to jack it, in order to relieve the DL from the transfer slab. Initially, we were going to specify that the structural steel column be cast in concrete (post jacking) per the prescriptive measures of the IBC. Contractor looked at the those requirements and said, "No" (because of the silly requirements for ties, and studs around the struc. steel).

So, now I need to sharpen the pencil to provide the minimum fireproofing detail required. The existing building, as I mentioned is Type I-B, which requires 2-hours for all primary structural members, and members have no additional protection other than the material that the structural elements are composed of. One part of me says that I need to treat this new column as Type I-A, and provide 3-hours of a gypsum board UL assembly, another part of me says, "The whole existing building frame is rated at 2-hours, that means I can wrap the steel column in 2-hours of gypsum board".

I think I may be misunderstanding a basic premise of fire resistance requirements of the code, which may be contributing to my confusion.