One layer 5/8” (15.9 mm) ToughRock® Fireguard C® gypsum board or 5/8” (15.9 mm) DensArmor Plus® Fireguard C® interior panels applied perpendicular to resilient furring channels with 1” Type S drywall screws 12” o.c. Resilient channels spaced 12” o.c. when insulation is used or 16” o.c. when no insulation is used. Resilient channels applied perpendicular to bottom chord of light-gauge steel trusses 48” o.c. with 1/2” Type S-12 screws. Optional glass fiber or mineral fiber batt or loose fill insulation applied directly over Toughrock Fireguard C gypsum board only. Trusses supporting 23/32” wood structural panel subfloor applied perpendicular to trusses with construction adhesive and mechanical fasteners 12” o.c. and 15/32” wood structural panel underlayment applied perpendicular to trusses with mechanical fasteners 12” o.c. Joints staggered between underlayment and subfloor.