[mmhendrie]

I'm tiling a shower ceiling, over a small space, joists actually 20" center to center. A friend told me for stability, I might want to first screw in to the joists 5/8" plywood where I would normally do ceiling board, then put ceiling board over the top. The plywood would allow me to put screws all over the ceiling board and add stability, so things don't fall on the person in the shower.

I like the idea, but are 2x6 joists strong enough to support the plywood, and the ceiling board, and the tile? I'm worried about the plywood being too heavy?

 

[Termite]

Your tile should be applied to 1/2" cementitious backerboard like wonderboard. You'd probably be smart to apply some plywood to the underside of the ceiling joists first. I certainly would not be concerned with the weight of the materials in such a small area unless there is a major structural deficiency with that ceiling's framing.

 

[Bob Mariani]

weight is not an issue. Be sure to seal all the seams and edges of the cement backer board used. 1/4" CBU should be fine if applied over plywood. (like a floor tile job). Use two coats of Redgard to assure waterproofing so the plywood does not delaminate in the future.

 

[mmhendrie]

thanks guys - i'm actually doing a schluter shower, the kerdi goes on over drywall and makes the whole thing water proof. It's not a steam shower, so I think i have a little flexibility on the ceiling - I can either kerdi it, or, perhaps just redguard the ceiling board and tile over that.

 

[Termite]

Good move on the Kerdi. That'll make life easier.