Hello there, I have ahome that is in need of a sub flooring in the bathroom. As I am pulling this up, they used compressed wood. Should I use plywood?
Plus, there is a rise in the center of the floor? Is this normal or what?

To eliminate the hump in the floor,you might remove the old flooring and look at the joists.One could have warped and you can then trim it.

A new plywood base and luan subfloor would be the proper method for a new surface.

KBC

I am with KBC to a point. In bathrooms I know there will be some water eventually. I put down a plywood sub glued and screwed to the joists and then top with Hardibacker 1/4" if you plan to install tile. Luan is kind of old school and never should be near water.