How does one replace the sub floor? I will redo the bathroom and need to get to the pipes under the sub floor. This is the first layer of flooring... so it is installed before the walls went up. Half the walls are over joists the the side walls are not. I am moving all the fixtures so I figured it would be easier to remove the subfloor, than cut a bunch of holes in the floor. I can get the old floor out. Pry in the middle and cut along the edges where the walls are. My real question is: DO I need to re-enforce the edges with 2 by's when I replace the subfloor? I really do not want the flooring to move or sag at the walls when I done. Is there another way?