what ply wood for flooring ?

[essex_lee]

Hi, would exterior 12mm ply be ok for tiling onto floor, its a small shower room, only 1m x 1m, will only get wet when someone steps out of shower.

There is currently floorboards down, i was going to take them up and put the ply straight onto the joists.

Thanks

 

[Gazzer]

No that is too thin to go onto the joists. Its ok to use to overboard but if onto joists then minimum 18mm.