Concrete slab for a shed
Type in your shed size and slab thickness, then choose a flat slab or a thickened edge. The answer comes back in cubic yards and bags.
How much concrete do I need for a shed base?
| Shed | Flat 4 in slab (yd³) | 80 lb bags | With thickened edge (yd³) | Bags or truck |
|---|---|---|---|---|
| 8 x 8 ft | 0.87 | 40 | 1.63 | Ready-mix |
| 8 x 10 ft | 1.09 | 49 | 1.96 | Ready-mix |
| 8 x 12 ft | 1.30 | 59 | 2.28 | Ready-mix |
| 10 x 10 ft | 1.36 | 62 | 2.34 | Ready-mix |
| 10 x 12 ft | 1.63 | 74 | 2.72 | Ready-mix |
| 10 x 16 ft | 2.17 | 98 | 3.48 | Ready-mix |
| 12 x 12 ft | 1.96 | 88 | 3.15 | Ready-mix |
| 12 x 16 ft | 2.61 | 118 | 4.02 | Ready-mix |
| 12 x 20 ft | 3.26 | 147 | 4.89 | Ready-mix |
| 16 x 20 ft | 4.35 | 196 | 6.19 | Ready-mix |
This thickened edge measures 12 in in width and 12 in in depth. Under the International Residential Code, it is the smallest permitted footing (IRC R403.1.1 and R403.1.4). The figures include 10% extra.
Flat slab or thickened edge
A garden shed usually sits on a flat slab that is 4 in thick. When you thicken the edge, the slab's outer foot becomes a footing. For a 10 by 12 ft shed, this adds about two thirds more concrete. The total is 2.72 yards rather than 1.63, so the job usually calls for a truck instead of bags.