Screw down plywood

Q: I am replacing the wood floors in our 45 yr. old house. As I started to remove the old strips, I was surprised to find them spanning 1″ x 2″ strips of wood (16″ O.C.) rather than attached directly to the subfloor. I would remove the strips and attach to the plank subfloor, but then the floor would be 3/4″ lower than it is now.

Can I reinstall the new floor to these strips or would I be better off removing everything and putting down a layer of plywood?

A: I would definitely screw down plywood. It will give you a much stronger, smoother surface to install your plank flooring on.