Garage & shed slab cost calculator
Estimate the cost of a poured concrete garage or shed slab from its area, your price per square foot, a thickened edge and any add-ons — with a contingency buffer.
Calculator
A 576 sq ft garage/shed slab at $7.00/sq ft with a thickened edge is about $4,875.20. A garage slab is concrete flatwork volume and cost only.
A garage or shed slab is a flatwork pour with one twist: the edge is usually thickened (a turned-down perimeter) so it can carry the walls and the loads that sit near them. This calculator prices the slab itself by the square foot, adds the thickened edge and any add-ons — vapor barrier, welded wire mesh, an apron at the door — as their own lines, and finishes with a contingency buffer.
Everything here is concrete flatwork cost only. A garage slab on this site is not a garage-door project and not a floor-covering install — it is the poured pad. The thickened edge is a cost line the contractor quotes, not a footing or foundation design; load-bearing edges and footings are set by a licensed engineer and local code.
Formula
The estimate sums the priced items and applies the contingency factor:
flatwork = area_sqft × price_per_sqft
subtotal = flatwork + thickened_edge + add_ons
total = subtotal × (1 + contingency%)
Thickened edge is the perimeter turn-down as quoted; add-ons capture the vapor barrier, mesh or apron; contingency is a fraction (0.10 = 10%).
Worked example
A 24 × 24 ft garage slab is 576 sq ft. At $7/sq ft with a $400 thickened edge, no other add-ons and a 10% contingency:
- Flatwork = 576 × $7 = $4,032
- Subtotal = $4,032 + $400 + $0 = $4,432
- Total = $4,432 × 1.10 = $4,875.20
So a typical two-car garage pad comes in around $4,875. A vapor barrier under a heated or finished space, wire mesh, or a thicker slab for a lift or heavy equipment will each add to that.
Thickness, vapor barrier & extras
Garage and shed slabs are usually poured a touch thicker than a plain patio — commonly 4–5" — because they carry vehicles, shelving and the wall loads at the edge. The slab-on-grade thickness reference lists the labeled planning bands; a professional confirms the right build for your loads. If you want the concrete quantity behind the price, the concrete calculator and sonotube / footing calculator turn your dimensions into cubic yards and bags.
Common extras worth entering as add-ons: a 6-mil vapor barrier under a slab you plan to heat or finish, welded wire mesh or fiber, a broom or trowel finish upgrade, control-joint cutting, and a small apron where the driveway meets the door. Price them individually so two bids can be compared honestly. As always, the cost bands are labeled planning guides — get itemized written quotes from licensed, insured concrete contractors before you commit.
Reference table
Labeled planning references for garage/shed pads:
| Item | Typical |
|---|---|
| Garage / shed slab thickness | 4–5" |
| Plain slab, installed | $5–$10/sq ft |
| Common two-car footprint | 24 × 24 ft = 576 sq ft |