Floor boards from hell!

[WookieOne]

Since i had central heating put in a few years ago the creaking from the upstairs floor boards is driving us insane !
They have cut the tongues off the boards and possibly this is where my creaking comes from although there are rows of chopped up and nailed back down boards now in every room upstairs.
I have tried screwing the boards down, ive filled them with talcum powder but still the beggers squeak so much its hard to concentrate on the TV downstairs.
What i was thinking was to lay sheets of plywood maybe upto 6mm deep over the top of floor boards to try and spread the load of people walking about upstairs.
Would this be a good idea and if so can someone advise on tips like i read to leave a 10mm gap around the edges for some reason.
Thanks

 

[freddiemercurystwin]

Is this chipboard? Personally I don't think adding 6mm ply will make much difference, really the lot needs replacing with T&G plywood and more screws than you've had hot dinners and you know it. You could try adding more screws ie every 150mm everywhere but without the tongues I cannot see how squeaks can be eliminated. you're just throwing good money after bad. Naturally adding all those pipes under the boards continuously heating and cooling the void albeit unavoidable obviously won't have helped.