Plywood on floor

[DaveOC]

Hi, I have moved into an old house, the floor boards are OK but a bit old Knackered and gappy, before I put in a fitted carpet I was going to cover the floor with plywood and screw down, my question is can I use thin ply ie 3mm, is there a down side to this or should I make it any thicker.
Or would hardboard be better?
Thanks for any advice.

 

[foxhole]

Hardboard is usually used under carpet.

 

[ETAF]

i put hardboard down on a couple of bedroom floors quite a few years ago, onto normal wood floor boarding , before underlay / carpet, all seemed fine, moved out of house since.

 

[DaveOC]

Thanks all, I'll use hardboard, should I use ring nails or screw them?

 

[foxhole]

Hammer stapler/tacker is easy option. Short ring nails if you don’t have tacker.