laying engineered flooring, question about surface under

happyhero

Hi I have bought some Engineered oak flooring and the guy in the shop sold me some silver sided foam stuff to go underneath. I explained to him it was for out bedroom on the 1st floor of our house and it was a joist and floorboards floor.

At the moment there is carpet and underlay which I will remove, under this there is hardboard sheets pined down and looking underneath this most of the floor is pretty good but there were a couple of high points which I removed the nails and played about with the joist underneath and the floorboard itself planing a little to get it to a reasonably level surface and screwing the floorboards back down.

My question is should I or can I leave the hardboard and put the foam underlay on top of this?

I was just thinking that maybe leaving the hardboard down gives an improved surface and maybe offers a little further insulation but I want to know if maybe there is a reason not to leave it in place or if it will be a better job without it for some reason, I basically want to do the best job possible.

The floor I am laying will be a floating floor the guy in the shop explained to me.

Any advice appreciated.

happyhero

pretty please

andyhop

I would leave the hardboard down. We often ply the subfloor prior to laying laminate and engineered floors. Timbermate excel is one of the better underlays