IBC Ch25: 5/8 Type X for 1-hr rated (per GA-600 fire assemblies). Screw spacing per GA-216. UL fire assemblies: U305 1-hr wood, U419 1-hr steel, U411 2-hr double layer. Level 4 finish: tape + 3 coats. Level 5: skim coat. Exterior sheathing: glass-mat (C1177) behind WRB.