I just wanted to post an update to my earlier questions concerning a new pine floor over old particle board. The subfloor/floor turned out to be sheets of 3/4 inch particle board. I followed your advice (Steve and JB) and ripped out the Particle board. I went ahead and am putting in a pine plank sub-floor using 1/2 inch pine tongue and groove boards. The plank sub-floor was definitely a lot more work than plywood but, when/if I renovate the room directly underneath the floor it will look good. I will finish with 3/4 inch pine flooring. The only question which I have is that in part of the room there is a non-structural drywall wall which is not not on the joists. In the other areas of the room I am able to stop the subfloor on the joists. Is there a way which I can put the plank sub floor all the way to this wall but not have the not have the end of the sub floor in between joists? I don't want to rip out and redo the wall. Any ideas? Thanks.