Well compacted, smooth subgrade is Part 1 in making successful slabs; Part 2 will cover formwork, joint details, vapor barriers and reinforcing.

A change in the actual thickness of the floor does affect the load-carrying capacity of the slab. For example, ... Designing Floor Slabs on Grade, 2nd Edition, The Aberdeen Group, 1996, pg. 184 .

If you live in a slab-on-grade, SOG, home or work in a similarly constructed commercial building, the air you breathe every day might well compare to what came out of that underground critter ...