What is the maximum ceiling-joist spacing for a shower area finished with tile on 5/8 inch gypsum board?

What is the maximum ceiling-joist spacing for a shower area finished with tile on 5/8 inch gypsum board?

• A. 12 inches
• B. 16 inches
• C. 18 inches
• D. 24 inches

Answer: (B)

When tiling a shower ceiling, the substrate must be stiff enough to carry the tile weight and resist movement in a wet area. A 5/8-inch gypsum board finish on its own is relatively flexible, so the joists need closer spacing to keep deflection under control. The maximum recommended spacing is 16 inches on center. Spacing anything wider would allow too much sag, risking cracked tile or grout and moisture-related damage to the gypsum board. The other options would be unnecessarily restrictive or unsafe for this substrate and application, so 16 inches on center is the appropriate limit.

When tiling a shower ceiling, the substrate must be stiff enough to carry the tile weight and resist movement in a wet area. A 5/8-inch gypsum board finish on its own is relatively flexible, so the joists need closer spacing to keep deflection under control. The maximum recommended spacing is 16 inches on center. Spacing anything wider would allow too much sag, risking cracked tile or grout and moisture-related damage to the gypsum board. The other options would be unnecessarily restrictive or unsafe for this substrate and application, so 16 inches on center is the appropriate limit.