creaky weyroc floor

[thedoberman1]

hi,having recently moved house our floorboards are driving me crazy,even tiptoeing upstairs can be heard downstairs,the floor is weyroc boards and is fixed down by 2" nails,what size screws should i replace them with? do they need to be a full threaded crew? et, please help!

 

[Burnerman]

For this I use Spax 5 x 50mm - pulls things down a treat.
Be absolutely certain not to put screws where you're unclear about pipe runs, but the existing nail position should give you a clue.
John