Can I lay underlay under hardboard?

Sounds a bit daft to me - underlay on wooden floorboards then harboard nailed on top and then, presumably some other layer on top of the hardbaord.

When the underlay perishes - which it surely will - you will have to take up the top covering and then the nailed-down hardboard, which will rip.

Harboard levelling is a reasonable idea if your suspended wooden floor is uneven but all the floor layers I've used have fitted plywood for levelling.

Don't understand "soundproofing" - is there a rock-band in the cellar?

The whole scheme appears at first sight to be aimed at using up the left over underlay - the soundproofing and comfort reasons are your justification. I doubt you will achieve either.

Consider the top surface you wish to walk on and use the appropriate material between that and the floorboards - Underlay is designed to go under carpet.

Richard Buxton
September 2008

Never heard of this before and it depends on the finished covering. Lino would be ok. Stick down pvc tiles may also be ok. But not ceramc floor tiles I think it would be un-stable and there would be too much movement. Wait for more replies you may get one from a floor layer. Wish I'd thought of that in my kitchen its a concrete floor.

Bob
September 2008

Sorry, I meant to say "the floor more sound-proof and comfortable to WALK on"!

THANKS

Adrianh
August 2008