Michael,
It has perimeter footings all the way around. The slab itself is 4" thick. The footer varies from (I think) 8" at the top of the grade to 19" at the lowest point of the grade. I think those numbers are right but I'm not really sure. The builder (slab only) quoted a flat fee of $3,000. Unfortunately (for him) he underestimated by about 1 1/2 cu yds of concrete and 1 load of dirt. I also have my doubts that the truck driver delivered as many cu yards of mix as he said he did. Maybe stopped at his grandmothers house on the way here

. The builder said rebar wasn't necessary with the fibermix concrete but I bought my own and had him install it anyhow. These were each 10' long, 1/2" diameter bent in a "U" shape and inserted into each corner between the anchor bolts. FYI the metal building is $7,500. It's 30' x 40', 10' walls with a peak in the center of about 14.5'. I had plumbing for a bathroom installed in one corner. Don't know if I'll use it (would have to install another ceptic tank) but I wanted it there just in case.
All in all, I should have less than $15,000 in it when totally completed. Keep in mind, all the interior work such as carpentry, electrical, HVAC, insulation, etc will be done by myself, family and friends.
OK, let's get started on yours!!!!
DD