A 4-inch concrete slab typically costs $6–$8 per square foot installed and a 6-inch slab $8–$10, based on HomeGuide’s 2026 national figures. A 10×10 ft shed pad runs about $600–$1,200 and a 20×20 ft garage-size slab about $2,400–$4,800. Size the slab to the load it will carry: sheds and patios usually take 4 inches, while RVs and heavy trucks need more.
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Slab costs by size
| Slab size | Area | Typical installed cost |
|---|---|---|
| 10×10 ft | 100 sq ft | $600–$1,200 |
| 12×12 ft | 144 sq ft | $860–$1,700 |
| 20×20 ft | 400 sq ft | $2,400–$4,800 |
| 20×30 ft | 600 sq ft | $3,600–$7,200 |
| 30×30 ft | 900 sq ft | $5,400–$10,800 |
Cost by thickness
| Thickness | Installed cost per sq ft |
|---|---|
| 4 inches | $6–$8 |
| 6 inches | $8–$10 |
| 8 inches | $10–$12 |
Sizing by use
| Use | Typical size | Typical cost | Notes |
|---|---|---|---|
| Shed pad | 100–400 sq ft | $600–$4,800 | Usually about 4 inches; often no reinforcement |
| Garage floor | 400–576 sq ft | $2,400–$6,900 | Usually reinforced, 4–6 inches |
| RV pad | 200–700 sq ft | $1,200–$8,400 | Thicker slab for the weight |
| HVAC pad | Small | Usually a small-job minimum | Many units sit on precast pads; ask whether a poured pad is needed |
Leave a margin around anything you build on the slab, so walls and doors don’t sit on the edge.
Thickness and reinforcement by load
- Foot traffic, sheds, patios: 4 inches is standard.
- Cars and light trucks: at least 4 inches, with thickened edges.
- RVs, trailers, heavy trucks: 5 to 6 inches. Concrete Network notes that going from 4 to 5 inches adds roughly 20% to the concrete cost but nearly 50% to load capacity.
- Reinforcement: wire mesh suits 4- to 5-inch slabs; #4 rebar on about a 12-inch grid suits 5 inches and up. Fibers reduce shrinkage cracks but aren’t structural.
Base preparation
A slab is only as good as what’s under it. Soft spots should be dug out, the subgrade compacted evenly, and a gravel base added where drainage is poor. Gravel for a base runs about $1–$3 per square foot. On Upstate red clay, that base matters: clay holds water, and water under a slab is what makes it settle and crack.
Level or slightly sloped? Pads that stay outside should shed water rather than hold it. Ask the contractor which way water will run.
Garage slabs vs. shed pads
A shed pad carries a light building and some storage; it is typically 4 inches and often unreinforced. A garage slab carries vehicles, so it is usually reinforced, 4 to 6 inches thick, with thickened edges. A garage with walls built on the slab also needs footings sized for the walls. If the building is a structure, see concrete foundations.
Permits for detached garages
Detached garages and larger accessory buildings usually go through a building permit. A simple shed pad may not. Rules differ inside the City of Greenville and in unincorporated Greenville County, so ask the permit office before you pour, and check HOA rules too.
How it works with us
- Tell us about the job. Fill in the short form with the service, your ZIP code and a rough size. Photos help.
- A local contractor calls you. We pass your request to a licensed contractor in our network who works in your area, usually within 24 hours.
- Get a free quote and decide. The contractor looks at the job and gives you a written quote. There is no cost and no obligation.
Concrete Pros Greenville SC is a free referral service. Work is performed by independent licensed contractors in our network.
Concrete slab questions
How thick should an RV pad be?
Plan on 5 to 6 inches, reinforced, on a compacted base. Concrete Network notes that going from 4 to 5 inches adds roughly 20% to the concrete cost but nearly 50% to load capacity, which is cheap insurance under a heavy vehicle.
Do I need rebar for a shed slab?
Usually not for a typical 4-inch shed pad, according to HomeGuide. Larger sheds, heavy equipment or a workshop with a vehicle inside are different; ask for wire mesh or rebar if the slab will carry more than light storage.
How long before I can use a new slab?
You can usually walk on it after one to two days. Wait one to two weeks before driving on it, and remember concrete keeps gaining strength until it is fully cured at about 28 days or more.
Related services and guides
Get a free quote from a local contractor
Tell us about the job once. A licensed contractor who works in your part of the Upstate will call you about a free, no-obligation quote, usually within 24 hours.
Request a free quote or call (864) 432-1750.
Sources
- HomeGuide: concrete slab cost (2026) — costs by size, thickness and use; reinforcement; gravel base; cure times.
- Concrete Network: concrete driveway installation essentials — thickness, reinforcement and subgrade guidance.
Prices are national 2026 ranges unless labelled local. How we research costs.
Last reviewed: October 2026