Shed Foundation Calculator

Price the right foundation for your shed before you build. Enter your shed dimensions, pick one of the four proven foundation types — concrete block piers, gravel pad, concrete slab, or skid — tell us your soil, and get exact material counts (blocks, cubic yards and tons of gravel, bags of concrete), a regional cost estimate, and a soil-based recommendation.

Calculate your shed foundation

The 4 shed foundation types, explained

A shed foundation has three jobs: keep the wood off wet ground, spread the load so the shed does not settle unevenly, and stay put for decades with minimal maintenance. Four designs cover nearly every backyard situation. Here is how each works, what it costs, and where it shines.

1. Concrete block piers

A concrete block shed foundation is a grid of piers made from standard 8x8x16 inch concrete masonry units (CMU), spaced 4 feet on-center under the shed's beams, with interior support rows every 6 feet of width. Each pier sits on a few inches of compacted gravel or leveling sand and is capped with a solid block so the beam bears flat. This is the most versatile foundation: because every pier is leveled independently, it handles clay soil (the floor framing stays above the wet zone with air circulating underneath) and sloped sites (taller stacks downhill, shorter uphill) better than any other option. Material cost is modest — about $162.40 for a 10x12 shed — and it is a genuine weekend DIY project with no concrete mixing. Its weakness is height: on very tall pier stacks you should mortar the courses or step up to poured piers.

2. Gravel pad

A gravel base for a shed is the cheapest and fastest proper foundation: 4 inches of compacted 3/4-inch crushed stone (6 inches on soft ground), extending 1 foot beyond the shed on all sides, laid over woven landscape fabric. The angular stone locks together under compaction, drains freely, and forgives minor ground movement. A 10x12 shed needs about 2.39 cubic yards — roughly 3.39 tons — plus 168 square feet of fabric, for around $219.90 in materials. Use crushed stone with fines, never pea gravel or river rock, which roll and never compact. The trade-off is longevity: expect to top up and re-level every 15 to 20 years, and do not use a gravel pad on a slope without retaining the downhill edge.

3. Concrete slab

A 4-inch concrete slab (6 inches for heavy equipment) is the permanent, do-it-once option: 40-plus year lifespan, perfectly level floor, and the best choice for a workshop with heavy machinery. For a 10x12 shed it takes about 1.63 cubic yards of concrete — either 74 bags of 80-lb premix or a short-load ready-mix truck (a ready-mix short load wins at this size) — plus 6x6 wire mesh, for roughly $304.95 in materials. The catch is skill and prep: the base must be compacted, forms must be level, and on clay you need a thicker stone base plus perimeter drainage or frost heave will crack it. It is also the foundation most likely to be treated as a permanent structure by your building department.

4. Skid foundation

A skid foundation uses pressure-treated 6x6 timbers laid directly on a shallow gravel bed, spaced no more than 6 feet apart, running the full length of the shed. Many prefab sheds are designed for exactly this. It is fast, cheap (about $300.00 in timbers for a 10x12), and the shed stays technically portable — useful where permits restrict permanent structures. Lifespan is 15 to 20 years before the timbers need attention, and it is best for small to mid-size sheds on flat ground rather than heavy workshops.

Which foundation is best for your soil?

Soil decides more than budget does. On flat, well-drained ground, a gravel pad is the best value — cheapest, easiest, and excellent drainage. On clay or wet ground, choose concrete block piers: they lift the framing above the moisture, tolerate heave, and keep air moving under the floor. On a slope, piers again — each pier adjusts to the grade, while a gravel pad would need retaining walls and a slab would need stepped formwork. The calculator's recommendation banner above applies exactly this logic to your inputs.

Shed foundation comparison (10x12 shed, US Midwest, 2026)

Costs are DIY material estimates computed by the calculator engine above. Contractor-installed prices typically run 2–3x materials.

Worked examples

Pro tips

• Always extend a gravel pad 1 ft past the shed on every side — it sheds roof drip away from the walls and gives you a clean working edge.
• Compact in lifts. Whether stone under piers or a full pad, compact every 2 inches. One thick loose layer settles; thin compacted lifts do not.
• Use crushed stone with fines, not pea gravel. Angular 3/4-inch minus locks together; round rock rolls forever. This is the single most common DIY mistake in a rock foundation under a shed.
• Keep wood 6+ inches above grade. Piers and skids both exist to break ground contact — backfilling soil against the beams defeats the purpose.
• Check the 120 sq ft rule. Many US jurisdictions exempt sheds under 120 sq ft (exactly a 10x12) from building permits, but setbacks still apply — and a slab reads as more permanent than piers or gravel if an inspector asks.
• Re-level check every spring. Walk the floor with a 4-ft level after the first freeze-thaw cycle; catching a settled pier early is a 10-minute shim job, not a rebuild.

Frequently asked questions

Material prices are 2026 US DIY averages before the regional multiplier; lumber and concrete prices move with local markets. This calculator sizes materials, not structural engineering — for sheds over 200 sq ft or in high-wind / seismic zones, follow local code and your shed manufacturer's anchoring specs.