plywood ceiling over shower
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?