In dwellings, the type of construction doesn't matter, and you can put it in dropped ceilings. [334.10(1) and 334.12(1)].
In multi-family dwellings, you can use it in type 3, 4 or 5, and you can put it in dropped ceilings. [334.12(2) and 334.12(2).
In commercial, you can use it in type 3, 4 or 5 construction, but you can't put it in a dropped ceiling. [334.10(3) and 334.12(2)].
E57: You can't change type of construction in the middle of a building. TOC governs the entire structure. See chapter 6 of the IBC.
