Concrete Slab Thickness Cheat Sheet
Recommended thickness, strength, rebar, and base prep for every common slab — on one printable page
Pouring a slab too thin is the single most expensive mistake a DIYer makes — cracked patios and crumbling driveways almost always trace back to insufficient thickness or a weak base. This cheat sheet gives you the recommended thickness, concrete strength (PSI), reinforcement, and gravel base for the slabs people pour most often, plus a yardage coverage table so you order the right amount.
Recommended Thickness by Use
| Application | Thickness |
|---|---|
| Walkway / sidewalk | 4 in |
| Patio | 4 in |
| Shed / outbuilding floor | 4 in |
| Garage floor (cars) | 4 in |
| Standard driveway (cars) | 4 in |
| Driveway (trucks / RV) | 5-6 in |
| Workshop / pole barn | 5-6 in |
| Footings / foundations | 6-12 in |
When in doubt, go one step thicker. The extra concrete is far cheaper than tearing out and re-pouring a failed slab.
Yardage Coverage (1 Cubic Yard)
| Slab Thickness | 1 cu yd covers |
|---|---|
| 4 in | 81 sq ft |
| 5 in | 65 sq ft |
| 6 in | 54 sq ft |
| 8 in | 40 sq ft |
Always order 5-10% extra for spillage, uneven subgrade, and over-excavation. Concrete is sold in whole or half yards.
Joints, Base & Curing Rules
| Rule | Value |
|---|---|
| Control joint spacing | 24-30x slab thickness |
| Control joint depth | 1/4 of slab thickness |
| Max joint panel | Keep panels near square |
| Vapor barrier | 6-10 mil poly |
| Rebar cover | 2-3 in from edges |
| Cure time (foot traffic) | 24-48 hrs |
Quick Volume Estimator
Fill in your slab to estimate cubic yards: (length ft x width ft x thickness ft) / 27. Remember thickness in feet = inches / 12 (4 in = 0.33 ft).