What is the best material for subfloor?
Plywood
A few builders say that they prefer OSB over plywood for flooring because the surface (when new) is always clean, flat, and knot-free. Simply put, many contractors find OSB to be a more consistent product than plywood or other types of material for subfloor: every sheet is the same.
Also, Which side goes up on OSB subfloor?
Answer. OSB roof panels should always be installed with the grade stamp facing into the attic and the screened surface (with the nail guide lines) facing up.