What should a shed sit on?

The four options

Gravel pad with skids (what our plans use)

Dig out the sod, lay 4 in of 3/4 in crushed gravel a foot bigger than the shed on every side, and compact it. The shed's floor frame sits on pressure-treated skids laid on the gravel. Water drains straight through, the wood never sits in mud, and the shed can be moved later. Use skids rated for ground contact.

Concrete blocks

Solid deck blocks or concrete blocks under the floor frame at each corner and along the middle. Fast and cheap on flat, firm ground, but each block must be leveled by hand, and blocks on bare soil can settle unevenly.

Piers

Concrete piers poured below the frost line, with post bases on top. The right choice on a slope or where frost heave is serious, and the most work of the four.

Concrete slab

A poured slab makes a permanent floor that takes a mower or a workbench. It costs the most, may need a permit even where the shed does not, and makes the shed a fixture.

Gravel and skids for common sizes

Sheds up to 16 ft deep sit on 4x4 skids; deeper sheds step up to 4x6. Wider sheds get a third or fourth skid so the floor joists never span more than 8 ft.

Getting the pad level

1. Mark the pad with stakes and string a foot outside the shed's footprint.
2. Dig out the sod and high spots so the pad is close to level before any gravel goes in.
3. Add the gravel in two layers, compacting each with a plate compactor or a hand tamper.
4. Set the skids and check them with a long level in both directions. Shim with stacked solid blocks, never with scraps of wood.
5. Measure the floor frame's diagonals before you nail the deck down. Equal diagonals mean a square shed.