Residential Building Inspector B1Building Planning and Life SafetyEasy
A homeowner is installing new interior gypsum board on walls and ceilings in a new addition. The wall studs are spaced 16 inches on center. What is the minimum nominal thickness of gypsum board required for these wall applications?
- A1/2 inch
- B5/8 inch
- C3/8 inch
- D1/4 inch
Show answer & explanationAnswer & explanation
Correct answer: C. 3/8 inch
According to the 2021 IRC, Table R702.3.5 Minimum Thickness of Gypsum Board, for walls with framing spaced 16 inches on center, the minimum nominal thickness of gypsum board is 3/8 inch (9.5 mm).
Why the other options are wrong
- A. 1/2 inch is a common thickness and is also acceptable, but not the minimum.
- B. 5/8 inch is typically used for fire-rated assemblies or for increased stiffness.
- D. 1/4 inch gypsum board is typically for curved surfaces or as a base layer in multi-ply applications.
Gypsum Board Wall Thickness
The minimum nominal thickness of gypsum board required for wall applications, determined by the spacing of framing members.
- Provides a finished surface and fire resistance.
- Thickness varies with stud spacing and specific use.
- Specified in IRC Table R702.3.5.
Memory trick: Gypsum board, three-eighths strong, when studs are sixteen, all day long.