The floor is poured as a 1 pc slab with 18 " deep walls around the outside. I wasn't sure that the cement would stay in wall forms if I tried to elevate the walls above the slab all in one pour. The wood has to be 8" above grade so you either have to pour a wall above grade or build up the slab with blocks. Most foundations are 3 pc, footings, walls, then floor, done sequentially. I saved about $1000 by doing just one pour.
MikeG