Adding tile flooring on second floor

[skyking1]

ERD,
I'm not there yet, but I previously repaired some flooring issues by my slider door before having wood floors installed.

I think it is 3/4" plywood in questionable condition. Built in 1984. I'm going to add more deck screws, and replace any damaged or delaminated plywood.

I could decide to add. 1/4" layer on top, or even replace all of it once I remove the tile.

The trusses are further apart than 16". I suspect 24" spacing.

Right now my plan is to screw down cement board.

Thanks for your comments.

That might be the whole issue then. 24" is not good for tile with 3/4 anything.
I'd use 1/2" plywood glued screwed down with the joints and orientation mixed, and then the Ditra uncoupler.