Does a concrete driveway need rebar?

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Every slab cracks as it shrinks, so the question is what happens after. On expansive clay an unreinforced driveway cracks, the cracks widen and step out of level as the soil swells and shrinks, water gets into the base, and the damage compounds. Rebar holds the pieces tight and at the same height. Spacing: #3 bars at 18 inches each way is the common residential spec, #4 bars at 18 inches suit heavier sections, and 24 inches is the widest spacing worth accepting on this ground. The cities use the tighter end for their own work; McKinney's 2026 residential drive approach detail calls for #4 bars at 18 inches each way on chairs in 6 inches of 4,000 psi concrete, and Sherman builds residential streets with #3 bars at 18 inches. Placement: bar lying on the dirt does almost nothing, so it sits on chairs at mid-depth, and that detail belongs in the written scope. Welded wire mesh: the National Ready Mixed Concrete Association notes that mesh will not prevent cracking but tends to keep cracks and joints from opening, and it only works as flat sheet held up in the slab, never as roll mesh walked into the bottom of the pour. Fiber: synthetic micro fibers at 1 to 2 pounds per cubic yard reduce plastic shrinkage cracking in fresh concrete, and macro fibers around 5 pounds per cubic yard can act as non-structural shrinkage reinforcement when the supplier documents their performance, which makes fiber a good companion to bar on clay rather than a replacement. Reinforcement is still the second line of defense; the first is a compacted base, because steel over soft fill only holds broken pieces together. The driveway thickness guide covers joints and base in detail, the thickness FAQ gives the quick numbers, and every concrete driveway scope here states bar size, spacing, and support in writing.