kitchen floor wonder?

[toxic]

ok so i've replaced the rotten joist now
i'm going to be laying floor tiles on it, i'll be putting 12mm wbp plywood on top of the floor boards but while i got the floor boards up?
1. shall i reinforce the joist with noggins inbetween?
2. can i screw the floor boards down screws instead of nailing them?

 

[mrgtv]

ok so i've replaced the rotten joist now
i'm going to be laying floor tiles on it, i'll be putting 12mm wbp plywood on top of the floor boards but while i got the floor boards up?
1. shall i reinforce the joist with noggins inbetween?
2. can i screw the floor boards down screws instead of nailing them?

12mm ply? Seems very thick.

1. Why?
2. Yes

 

[toxic]

oh, i thought it had to be 12mm thick? everywhere i've looked it said 12mm. do you think i'll get away with 9mm or 6mm?
my mate layed a tile floor with 9mm under the tiles and some tiles cracked.