Time for some educating...

[Peter]

Agree, if it's properly prepared and using the correct adhesives, it's still possible to successfully tile to ply. There's more ideal systems now but just because it's ply doesn't mean that the tiles will fall off in 3 months.

 

[peteablard]

I've done loads of commercial jobs directly onto ply, if I didn't someone else would! Mostly floors, a few walls, wouldn't do it in a wet area though.

 

[Stef]

I think the problem we have with ply now is that it's getting shipped from China cheap as chips & to be honest most of it is garbage.
Most of it delaminates & as stated we now have a lot better materials to work with..