What is the maximum spacing of ceiling joists in a shower area when using 5/8 inch water-resistant gypsum board with tile installed using adhesive?

What is the maximum spacing of ceiling joists in a shower area when using 5/8 inch water-resistant gypsum board with tile installed using adhesive?

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

Answer: (D)

Support and stiffness of the ceiling substrate when tiling a shower ceiling are being tested. A 5/8 inch water‑resistant gypsum board is used as the tile substrate, and tile is attached with adhesive, so the weight of the tile and the adhesive adds load that the joists must carry without excessive deflection. To keep the ceiling stiff enough and prevent sag or tile/grout cracks, the joists should be spaced close enough. The maximum practical spacing for this setup is 16 inches on center, which limits deflection to within typical tile installation requirements. Wider spacing, such as 18 inches or 24 inches, would allow more sag and risk failures, while 12 inches would be more conservative than needed. So the best choice is 16 inches on center.

Support and stiffness of the ceiling substrate when tiling a shower ceiling are being tested. A 5/8 inch water‑resistant gypsum board is used as the tile substrate, and tile is attached with adhesive, so the weight of the tile and the adhesive adds load that the joists must carry without excessive deflection. To keep the ceiling stiff enough and prevent sag or tile/grout cracks, the joists should be spaced close enough. The maximum practical spacing for this setup is 16 inches on center, which limits deflection to within typical tile installation requirements. Wider spacing, such as 18 inches or 24 inches, would allow more sag and risk failures, while 12 inches would be more conservative than needed. So the best choice is 16 inches on center.