How can I stop cracking/squeaking sounds while leveling this floor?

Question

I am reconditioning a wooden floor; I pulled up the carpet and am repairing, levelling and then painting the so-so boards I found. I already tried replacing the nails with screws but found that the boards are pretty noisy. Not so much squeaky as cracking sounds if you know what I mean.

There's a lot of wood added to the original joists because the house is very old - both alongside the joists and as 'noggings' (been looking at this guide). It's cheap ply and I think this is causing it.

As I have to level it anyway I can put some material between the two layers (there was a load of scrap wood slivers there currently). I read you can use cardboard or plastic too. As I want to maximise the quietness I had the brainwave of using a layer of thick carpet underfelt - not the foamy stuff but wool or felt.

What do you think of this idea and does anyone know the best material for levelling to reduce noise?

Answer 1

Most any material that keeps the wood to wood contact to a minimum should work. The most common material used is red rosin paper, but asphalt paper used to be an old favorite. I would avoid any thick absorbent materials like untreated felt or open cell foam, as they can absorb moisture or water and become moldy. Use screws whenever possible instead of nails, as nails will squeak as they become loose as wood shrinks around them. If you have to use nails, be sure to use threaded/ring nails to minimize this potential problem.