Commercial Building Inspector B2Wall Construction and Wall CoveringsHard
A commercial building inspector is reviewing the specifications for a new 1-hour fire-resistance-rated interior wall constructed with cold-formed steel studs. The wall is 12 feet (3658 mm) high. What is the minimum flange width required for 3-5/8 inch (92 mm) 20-gauge cold-formed steel studs used in this wall assembly?
- A1-3/8 inches (35 mm)
- B2 inches (51 mm)
- C1-5/8 inches (41 mm)
- D1-1/4 inches (32 mm)
Show answer & explanationAnswer & explanation
Correct answer: A. 1-3/8 inches (35 mm)
For 3-5/8 inch (92 mm) 20-gauge cold-formed steel studs in a 1-hour fire-resistance-rated interior wall up to 12 feet (3658 mm) high, the minimum flange width required by AISI S100-16 (referenced by IBC) and common industry practice for fire-rated assemblies is 1-3/8 inches (35 mm). This ensures stability and proper fastening for fire-rated gypsum board.
Why the other options are wrong
- B. 2 inches is typically for wider studs or specific structural applications.
- C. 1-5/8 inches is a common flange width but not the minimum for this specific scenario.
- D. 1-1/4 inches is generally for non-fire-rated applications or specific non-structural studs.
Cold-Formed Steel Stud Flange Width
The minimum flange width required for cold-formed steel studs in fire-resistance-rated walls, based on stud depth, gauge, and wall height.
- Flange width affects stud stability and fastening capacity.
- Fire-rated assemblies often require specific flange widths for proper gypsum board attachment.
- AISI S100 (North American Specification for the Design of Cold-Formed Steel Structural Members) is the primary reference.
Memory trick: CFS flange: fire's fight, keep it tight.