IBC Design 721.1(3) 22-1.1

1-Hour Fire Rated Steel joists, floor trusses and flat or pitched roof… — Base layer 5/8" Type X gypsum board applied…

IBC Table 721.1(3), Item 22-1.1: Steel joists, floor trusses and flat or pitched roof trusses spaced a maximum 24" o.c. with 1/2" wood structural panels with exterior glue applied at right angles to top of joist or top chord of trusses with No. 8 screws. The wood structural panel thickness shall be not less than nominal 1/2" nor less than required by Chapter 23.. Ceiling: Base layer 5/8" Type X gypsum board applied at right angles to steel framing 24" on center with 1" Type S dry wall screws spaced 24" on center. Face layer 5/8" Type X gypsum board applied at right angles to steel framing attached through base layer with 1-5/8" Type S dry wall screws 12" on center at end joints and intermediate joints and 1-1/2" Type G dry wall screws 12 inches on center placed 2" back on either side of face layer end joints. Joints of the face layer are offset 24" from the joints of the base layer. Minimum slab thickness — 1-hr: Varies". Minimum ceiling thickness — 1-hr: 1-1/4". Prescriptive assembly from the adopted building code — see table footnotes for conditions.