Small shed footings?

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!

I did the same thing several years ago that you are thinkin of doing. Instead of concrete piers I just used treated 6x6's sunk in the ground at 4 foot spaceings 2 feet in the ground. We get alot of wind and frost here and I have not had any problems so far. I'm sure concrete would be more perminent but by the time those 6x6's rot off I wont be around to haveta worry bout it.

the frost line in NJ is 48'' ????...seems like its kinda deep

here in northwest ct we only have a 42 " frost line

if i were you i'd go with your idea of going a couple feet and calling it good

Actually I think you're right-it's 42" here too, but just the same, that's a lot of digging! I'm thinking I might do what butcher said and bury some 6x6s 2' deep or so pole barn style.

Why not just a few concrete blocks
as they settle use a bottle jack to sneak in shims on top of the blocks that need it

avoiding a shed tax ?

Use concrete deck blocks and let the shed float just like a freestanding deck.

No need to dig holes.

X3 with the blocks, just shim as needed.

42" seems VERY conservative, but I would agree. Typically sheds of this size are not place on frost free foundations so doing something that can be adjusted after the spring thaw makes more sense.

Adjustable pier blocks work?
You can get an adjustable bolt & clamp to raise & lower the ""U" strap

I'd do the blocks - just put higher posts on top for the lower shed & brace the posts well.

I'd remove the topsoil/sod & replace with gravel under them though - unless there's already gravel there.