30x40 Concrete Slab Cost: 2026 Pricing for Garages, Shops, and Sheds
Estimate the cost of a 30x40 concrete slab in 2026. See concrete yardage, thickness, reinforcement, finish, labor, and site prep cost ranges.
How Much Does a 30x40 Concrete Slab Cost?
A 30x40 concrete slab is 1,200 square feet. In 2026, a typical 30x40 slab costs $7,200 to $18,000 installed for a basic 4-inch slab, and more if it needs thickened edges, rebar, vapor barrier, grading, or a polished finish.
Use the Concrete Cost Calculator to calculate cubic yards from your exact length, width, thickness, and extra percentage.
Concrete Yardage for a 30x40 Slab
| Slab thickness | Concrete needed before extra | Suggested order with 10% extra |
|---|---|---|
| 4 inches | 14.8 cu yd | 16.3 cu yd |
| 5 inches | 18.5 cu yd | 20.4 cu yd |
| 6 inches | 22.2 cu yd | 24.4 cu yd |
For garages, shops, and heavy equipment areas, ask a local contractor or engineer whether 4 inches is enough. Vehicle loads, soil, and building code requirements can change the thickness and reinforcement.
Installed Cost by Slab Type
| Slab type | Typical cost |
|---|---|
| Basic 4-inch broom-finished slab | $7,200 - $12,000 |
| Reinforced slab with wire mesh | $8,500 - $14,000 |
| Rebar-reinforced garage or shop slab | $10,000 - $18,000 |
| Slab with thickened edges | $12,000 - $22,000 |
| Decorative or polished finish | $14,000 - $30,000+ |
Cost Breakdown
| Line item | Typical cost |
|---|---|
| Concrete delivery | $2,000 - $4,500 |
| Base gravel and compaction | $1,200 - $4,000 |
| Forms and layout | $800 - $2,000 |
| Reinforcement | $800 - $3,500 |
| Labor and finishing | $3,500 - $9,000 |
| Vapor barrier or insulation | $500 - $2,500 |
| Permits or inspection | $100 - $800 |
What Raises the Cost?
Site prep is often the surprise. Poor soil, tree roots, bad drainage, excavation, fill, and access limitations can add thousands of dollars before the pour starts.
Thicker slabs and reinforcement also matter. A patio slab is not the same as a garage or shop slab. A structure that supports vehicles, lifts, or heavy storage may require more concrete, rebar, thickened edges, or engineered specifications.
Related Estimates
If your project is smaller, compare the 20x20 concrete patio scenario or the 10x10 concrete slab scenario. If your project is a driveway, use the concrete driveway cost scenario.
FAQ
How many yards of concrete are in a 30x40 slab?
A 4-inch 30x40 slab needs about 14.8 cubic yards before waste. Ordering around 16.3 cubic yards gives a 10% extra allowance.
Is 4 inches thick enough for a 30x40 slab?
It may be enough for some light-use slabs, but garages, shops, and heavy loads often need additional reinforcement or thickness.
Can I pour a 30x40 slab myself?
Most homeowners should hire a concrete crew for a slab this size. Timing, finishing, level control, and truck coordination are difficult at 1,200 sq ft.
*These are national planning ranges as of July 2026. Always confirm structural requirements locally before pouring a garage, shop, or building slab.*