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, John

ps, I posted this before and the only suggestion I got was to put cork
expansion joints which gave a small improvement

On 20 Mar, 09:08, wrote:
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, John

ps, I posted this before and the only suggestion I got was to put cork
expansion joints which gave a small improvement

I had a similar problem having laid hardboard over old floorboards in
order to lay cushioned vinyl on top. The hardboard was nailed down and
the nails pulled slightly as the hardboard deformed due to the cupped
floorboards.
Have you screwed just into the boards below ? Longer screws into the
joists would be better. Also, I would try a thin layer of rubber (like
the thin laminate underlay) between the floorboards and the plywood.
You could always remove the old boards completely of course. More work
tho'
Simon.