A concrete driveway should be 4 inches thick for cars and pickups and 5 to 6 inches wherever trucks, trailers, or RVs load it, over 4 to 6 inches of compacted base. McKinney and Sherman build their own residential concrete at 6 inches.
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Thickness follows the heaviest load that will regularly cross the slab, not the average one. Four inches over a compacted base carries daily cars and pickups for decades, while 5 to 6 inches belongs at the apron where a trailer swings in, the pad where a boat, RV, or tractor parks, the run to a shop door, and the first stretch off the road where delivery and concrete trucks turn; thickening those areas at pour time costs far less than replacing a cracked 4-inch section later. The cities in this corridor show what they trust on this clay. McKinney's 2026 standard detail for the residential drive approach inside the right-of-way calls for 6 inches of 4,000 psi concrete with #4 bars at 18 inches each way on chairs, inspected before the pour, and Sherman's engineering manual builds residential streets at 6 inches with #3 bars at 18 inches over 8 inches of lime- or cement-treated subgrade. A private drive does not have to match a street, but those numbers are a useful yardstick when one bid says 3.5 inches. Two companion specs matter as much as the inches. The base: thickness cannot rescue a slab poured on loose or wet clay, so subgrade preparation and compacted flex base belong in the written scope. The joints: the National Ready Mixed Concrete Association recommends spacing of 24 to 36 times the slab thickness, about 10 feet for a 4-inch slab and never more than 15, with grooves cut to at least a quarter of the depth. Concrete in the 3,000 to 4,000 psi range with rebar on chairs completes the spec. The full driveway thickness guide walks through each piece, and the driveway service in McKinney states thickness by area in every written scope.