CSLB General Building (B)Finishes and Building EnvelopeMedium
A contractor is installing 5/8-inch Type X gypsum board on a garage ceiling that requires a one-hour fire-rated assembly, with framing spaced 24 inches on center. What is the maximum required screw spacing along the field of the board (not at edges)?
- A7 inches on center
- B12 inches on center
- C16 inches on center
- D24 inches on center
Show answer & explanationAnswer & explanation
Correct answer: B. 12 inches on center
For fire-rated ceiling assemblies with framing at 24 inches on center, code and manufacturer fastening schedules typically require screws spaced at 12 inches on center in the field to maintain the integrity of the fire-resistive rating.
Why the other options are wrong
- A. Too tight; not the standard field spacing for this assembly.
- C. This spacing is common for walls, not fire-rated ceilings.
- D. Too widely spaced to maintain fire-rated ceiling performance.
Fire-Rated Ceiling Fastening
Fire-rated gypsum ceiling assemblies require tighter fastener spacing than standard walls to maintain structural integrity during a fire.
- 12 inches o.c. typical field spacing on rated ceilings
- Framing spacing affects required fastener spacing
- Edge/perimeter spacing often tighter than field
Memory trick: 'Ceilings need closer screws to hold the fire fuse.'