My wife is currently getting quotes for oak hard wood flooring for the first floor of our 100 year old house. For 3/4's of the job, no problem, it will be placed over old hard wood. The rest of the floor is a problem, one contractor says he will not put flooring over a chipboard underlayment. (small pieces of scrap lumber glued and pressed into 4 x 8 sheets) The other contractor says, as long as he puts tarpaper between the underlayment and hardwood, there is no problem. Each contractor has over 20 years of experience. Any comments on who is correct would be appreciated.