IBC Design 721.1(3) 21-1.1

1-Hour Fire Rated Wood joists, wood I-joists, floor trusses and flat or… — Base layer 5/8" Type X gypsum wallboard…

IBC Table 721.1(3), Item 21-1.1: Wood joists, wood I-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 8d nails. 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 wallboard applied at right angles to joist or truss 24" o.c. with 1-1/4" Type S or Type W drywall screws 24" o.c. Face layer 5/8" Type X gypsum wallboard or veneer base applied at right angles to joist or truss through base layer with 1-7/8" Type S or Type W drywall screws 12" o.c. at joints and intermediate joist or truss. Face layer Type G drywall screws placed 2" back on either side of face layer end joints, 12" o.c. 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.