Rough boards, plywood, flakeboard, or oriented strand board laid on top of the floor joists, to which the finish floor is fastened.
The sheathing, usually made of plywood, placed on top of floor joists and covered by flooring.
A wood or fibrous material that is nailed to the floor joists and then receives the finished flooring.
Certain material, like plywood, that is installed on the floor joists of a building or structure, onto which the walls and finished flooring is attached.