I just bought a house that has crawlspace fundation. I am going to install floating stranded bamboo floor and I have purchased 3-in-1 underlayment for the bamboo floor. When I ripped out the old carpet I noticed the previous owner had compressed board between the carpet underlayment and the wooden subfloor, needless to say I ripped the compressed boards out since some were stained pretty bad.

Now I am hearing mixed advices about if I can just lay the underlayment on top of the bare wooden pine floor (3/4"), and put the bamboo flooring over the underlay.

My handyman friend say to put felt paper, and other person say to put plywood. I also read about putting OSB (since it is cheaper) but so far I am lost about if I should install boards over the subfloor.

Any suggestions?

Thanks