How Much Concrete for a 10x12 Shed Slab?

How much concrete for a 10x12 shed slab works out to about 1.48 cubic yards at 4 inches thick. That is roughly 67 bags of 80-pound mix, or a small ready-mix order of about 1.75 yards once you add a cushion. A 10 by 12 foot shed is one of the most common backyard sizes, and its slab sits right on the line where bags are possible but a truck starts to look appealing.

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Slab volume

The footprint is 120 square feet.

Thickness	Cubic feet	Cubic yards	80 lb bags	60 lb bags
4 inches	40	1.48	about 67	about 89
5 inches	50	1.85	about 84	about 112
6 inches	60	2.22	about 100	about 134

Bag counts assume about 0.6 cubic feet per 80-pound bag and 0.45 per 60-pound bag. Add 5 to 10 percent for waste.

Do you need a thickened edge?

A shed slab is often poured with a perimeter that goes a bit deeper than the floor, which stiffens the edge where the walls sit. A modest edge 8 inches wide that drops 4 inches below a 4-inch floor adds about 44 feet × 0.667 × 0.333 = 9.8 cubic feet, or roughly 0.36 cubic yards. That pushes a 4-inch slab to about 1.85 yards before waste. Some areas require footings for any permanent structure over a certain size, so check with your building department first.

Slab, gravel pad, or blocks?

Concrete is not the only foundation for a shed. A gravel shed foundation drains well, costs less, and suits most wood sheds with a built-in floor. A slab makes more sense when:

The shed has no floor of its own and the slab is the floor.
You plan to park a mower, ATV, or motorcycle inside.
You want a workshop with a smooth, sweepable surface.
The shed will hold heavy items such as a safe or a stack of building materials.

Bags or a truck for 1.5 yards

At 67 or more 80-pound bags, you are lifting about 2.7 tons. With a rented mixer and two or three helpers, it can be done in a long morning, but the work has to keep moving so each batch blends into the last. A short-load ready-mix delivery costs more per yard, yet it puts all the concrete down at once and leaves you free to focus on screeding and finishing. If the truck cannot reach the shed site, ask about a small line pump or plan for several wheelbarrows and helpers.

Base and prep

A 4-inch compacted crushed stone base under a 10x12 slab takes 40 cubic feet, or about 1.5 cubic yards. That is roughly 2.1 to 2.25 tons of stone. Spread it in two layers and compact each one with a plate compactor. Set forms with 2x4s or 2x6s staked every few feet, and check that the diagonals match so the slab is square. A vapor barrier over the base is common if the shed will store things that do not like moisture.

Finishing details

Anchors. Set J-bolts or plan for wedge anchors so the shed can be fastened down.
Slope. A very slight pitch toward the door, around 1/8 inch per foot, helps water run out.
Joint. One control joint across the 12-foot direction, at the midpoint, helps on a 4-inch slab.
Curing. Keep the slab damp or covered for several days and wait at least a week before setting heavy walls or contents on it.

Questions people ask

How many yards of concrete for a 10x12 shed slab?

About 1.48 cubic yards at 4 inches thick, 1.85 at 5 inches, and 2.22 at 6 inches, plus 5 to 10 percent for waste.

How many bags of concrete for a 10x12 slab?

About 67 bags of 80-pound mix or 89 bags of 60-pound mix at 4 inches thick, before waste.

How thick should a shed slab be?

Four inches on a compacted gravel base is common for typical sheds. Use 5 to 6 inches if you will park a mower, ATV, or other heavy equipment inside.

How much gravel goes under a 10x12 shed slab?

About 1.5 cubic yards for a 4-inch base, roughly 2.1 to 2.25 tons of crushed stone.

Is a gravel pad better than a concrete slab for a shed?

For a wood shed with its own floor, gravel often works well and drains better. A slab is better when it serves as the floor or the shed holds heavy equipment.

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