I am planning to install 5/8 in. plywood underlayment for some floating 1/4 in. cork plank flooring. Unfortunately, there is a hump in the floor spanning three joists, based on my measurement and estimation. So I need to flatten out that hump somehow for the flooring.
I believe our joists are 2x8 in., 16 in O.C. Those three joists appear to be ~5/8 in. higher than the remainder of the joists in the room. The subfloor is 5/8 in. plywood.
I'm wondering how best to handle the hump. Should I cut and rip the subfloor to get access to the floor joists and sand/plane 5/8 in. off of each joist? Should I sand the subfloor down to virtually nothing? Should I just install the underlayment plywood overtop of the subfloor, then sanding the underlayment down to virtually nothing?
My worries for each scenario:
- Would shaving 5/8 in. off of a 2x8 beam risk its structural integrity too much?
- Would sanding the subfloor down to virtually nothing in the high spots basically destroy the subfloor and it's integrity?
- If I sand underlayment down to virtually nothing, how would I attach the extremely thin portions of the underlayment to the full-thickness subfloor that would most likely splinter/split if screwed with wood screws?
I don't think I want to use self-leveling compound for the entire room in case I want to rip the flooring out of the room in the future.
How would you all recommend dealing with this hump?