I have old floorboards in my kitchen on which I have laid 3 sheets of
6 * 4 (feet) ,12mm plywood as I want to put down vinyl. However even though the floorboards didn't seem to squeak , the plywood laid on top does no matter how many screws I put in! Is this a known problem with plywood? Part of the problem may be that I've replaced sections of the old floorboards which were damaged with new boards which may be a fraction thinner/thicker. Is it possible to put something like carpet underlay/thick cardboard/ anything else between the ply and floorboards to stop the squeaking? Thanks, Johnps, I posted this before and the only suggestion I got was to put cork expansion joints which gave a small improvement