I'm putting up two small (8x12) sheds in my back yard toward the rear of the property where the ground is kind of uneven and it tends to get a little wet too. I'd like both sheds to sit at the same height despite the fact that the grade is maybe 12-18" higher on the right side than the left side (they will sit 24' apart), so doing a simple foundation of leveled gravel and 6x6 skids probably wouldn't work that well for the one that sits lower since it would require a HUGE amount of gravel. I thought about pouring piers instead and setting 6x6 skids on top of those, which would act as the girders for the floor joists. On the right side the piers would barely stick out of the ground, but on the left side (12-18" lower) I would build them up with sonotubes to the necessary height. I'm just not sure how deep to go. There is no code to deal with-sheds under 100 SF are not subject to any kind of inspection or permitting process here. The frost line here (Northern NJ) is nearly 48" deep-do I really need to go that deep for an 8x12 shed? Not having to do so and only going say 2' below grade would save a lot of labor and concrete!