What is the name of the layer of floor that rests on top of the joists and supports all layers above it?

The subfloor is the flat surface that is positioned on top of the joists that supports all layers on top of it (second only in support to the joists). This layer is typically made of plywood or OSB. If the floor is a concrete slab, then the concrete slab is considered the subfloor.

Asked by Jason Forbes · Last updated 5 years ago · 132.1K views · SOURCE