been doing a lot of reading and this site has tons of great resources!

i want to put 3/4" nail down hardwood flooring in my house. ripped up the carpet and to my dismay i found 5/8" particle board (the oatmeal stuff) over 1/2" plywood. i've read enough to know that particle board is not sufficient underlayment for hardwoods. i've spent the day ripping that stuff up and luckily it wasn't glued down and the subfloor looks to be in decent shape.

my question is what options do i have as far as underlayment and how thick do i need to go?

thanks!

you should go with at least 1/4" to bring you to 3/4" but I would go as thick as you can without causing height problems, the thicker the subfloor the more solid it will be .

thank you very much for the reply. couple more q's...

do i need to put any paper overtop the subfloor? i know i will need a vapor barrier between the underlayment and the hardwood flooring, i'm just not sure if i need it between the subfloor and underlayment too.

also for the underlayment, should i use osb? are there other options?

I don't use paper between layers. Plywood is a better option over OSB.