The most common storage shed foundation are the wooden skid and the concrete slab.
I built this storage shed on a skid foundation, it's easier and cheaper to construct, and it allows you to move the storage shed if you need to.
How to build a storage shed
Material for the foundation.
2- 4x4x8 treated pine for the skids.
2 2x4x8 treated pine for bands.
7 2x4x93" treated pine for floor joist.
2 3/4" plywood 4x8 for floor decking.
I measured 7- 2x4 to 93" for floor joist and 2- 2x4x8 for bands.
I cut 7 -2x4 to 93" for floor joist and 2- 2x4x8' for bands
Position your joist approximately 16" apart.
Nail through the bands and in to the end of the joist.
Position your skids so joist hang over about 16" beyond the skids. I will be setting my storage shed on concrete bocks. If you want to set it down with no concrete blocks you should prepare a gravel base. To do this remove 4"of soil in an area about 12" wider and longer than your dimension of the storage shed. Fill in the area with 4" of compactible gravel. check for level using a 4 foot level and 8 ft long 2x4. rake until it is fairly level. Tamp the gravel using a hand tamper, check for level, add or remove gravel until the surface is level.
Tonail the joists to skids.
Level the floor, lift the frame where it's low, add treated 2x4 or whatever you need to get it leveled.
Measure diagonally across the floor to square it. Shift the frame until both sides measure the same both ways.
Lay your plywood and nail it.