Concrete slabs are not the "finish floor" itself (i.e., vinyl, wood, carpet, etc.), but the foundation base below the finish floor and any substrate.
The concrete slab is usually about 4 inches or greater in depth. Its advantages over other types of foundations:
- A level surface.
- A solid surface.
- Resists compression of soil from outside of the foundation.
Examples: The builders laid down a concrete slab floor foundation before proceeding with the framing.