You will have to make sure your joists can handle the addition of considerably more weight from the plywood subfloor and any floor coverings.
How to level old wood floors.
Hardwood floor installers often use the term level when referring to subfloors when actually they are meaning the term flat while it s desirable to have a level floor most homes.
A plywood subfloor will bridge any minor waves in the existing floor and leveling compound would help too.
On the top side of the floor another fix it idea to lay down new hardwood over the existing floor.
When installing a hardwood floor the homeowner may need to level the existing subfloor.
When complete this will be a spacer that bridges the gap between the old floor and the new level surface.
Adjust the strip as needed.
This will expose the subfloor underneath which is where most leveling problems lie.
If you re replacing an old floor with a new one your first task will be to get rid of the outdated flooring material.
Position the leveling strip on the floor and see if the top edge of the strip checks out as level.