How Thick Should a Concrete Slab Be?
Quick answer
Use 4 inches for patios, sidewalks and shed floors. Step up to 5–6 inches for driveways and anywhere vehicles or heavy equipment will sit.
Slab thickness is driven by the load it carries. Too thin and it cracks; too thick wastes concrete. These are the standard minimums.
| Application | Thickness |
|---|---|
| Walkway / sidewalk | 4 in |
| Patio | 4 in |
| Shed / garden floor | 4 in |
| Standard driveway (cars) | 4–5 in |
| Driveway (trucks, RVs) | 5–6 in |
| Garage floor | 5–6 in |
A compacted gravel sub-base and proper control joints matter as much as thickness for preventing cracks.