Leveling Subfloor and/or Joists
I’m installing engineered hardwood in my master bedroom (second floor, converted attic space) and am trying to get my subfloor level. It is for the most part, but the middle of the room has a hump I have to lower.
The room used to be carpeted and I found a layer of 1/2” particle board underlayment underneath with a layer of 3/4” subfloor underneath the underlayment. I was hoping the hump was just swelling in the underlayment, but it followed through to the subfloor. After pulling a few subfloor boards, I see the hump exists in the joists where they appear to be sistered at the midpoint of the building.
I’m looking for ideas on the best plan forward. At first I assumed the joists were crowned and that I could plane them down a bit to get them level, but now I’m wondering if it would be easier (and more stable) to try sanding down the subfloor boards instead. Any ideas?