Driveway Thickness for Trucks and RVs in Central Texas
Last spring I set up in the street in Mueller and, while the boom was folded, watched the owner two houses down park a 34 foot Class A motorhome. It cleared the apron fine. Then the rear duals came onto the 4 inch slab and you could see the panel flex—the joint opened, closed, and stayed a hair out of line. Eight-year-old driveway. Never going to hold that.
I drive a five-axle boom pump that leaves the yard around 70,000 lb, so I take an interest in how thick driveways are.
Start with the axle load, not the vehicle
Concrete does not care what the vehicle weighs. It cares what comes through one axle onto one patch of slab.
- Loaded one-ton dually with a trailer: 11,000 to 14,000 lb gross, 7,000 to 9,500 lb on the rear axle.
- Class A motorhome, 32 to 40 feet: 26,000 to 36,000 lb gross, 15,000 to 20,000 lb on the rear axle.
- Loaded ready-mix truck: 66,000 to 80,000 lb gross, 17,000 to 20,000 lb on each rear axle.
A 4 inch slab of 3,000 psi concrete with no steel has a modulus of rupture around 410 psi. It carries a car axle over a good base all day. It will not survive that same load near a free edge or a corner—exactly where an RV parks, and where support under an Austin slab disappears first.
It is a support problem before it is a concrete problem
Most of Austin east of MoPac sits on Blackland Prairie clay that measurably changes volume with moisture. It swells in a wet spring, shrinks in a dry August, and the movement is not uniform—slab edges dry faster than the middle, so the panel ends up bridging a hump or spanning a void. That is a bending load on something bad at bending, and we break it down in our piece on what expansive clay does under Austin driveways.
Mueller has its own wrinkle: built over the old municipal airport, so what sits under a lot ranges from native clay to engineered fill to crushed remnants of the airfield paving. The fix is not exotic—strip the topsoil, moisture-condition the clay 2 to 4 percent above optimum so it is already swollen rather than thirsty, compact to 95 percent standard Proctor, then bring in 6 to 8 inches of crushed base in lifts over a separation fabric.
The spec that actually holds trucks
- 6 inches thick, not 4. Fifty percent more concrete, roughly doubling what the panel carries.
- 4,000 to 4,500 psi at 28 days, 4 to 5 inch slump at the truck. Nobody adds water on site beyond what the ticket allows.
- #4 rebar at 18 inches on center each way, on chairs at mid-depth. Mesh raked up off the ground is not reinforcement, and fiber controls shrinkage cracking without replacing bar for load.
- A thickened edge—a turndown 12 inches deep by 12 wide at the outside edges and apron.
- Control joints at 12 to 15 feet, saw cut a quarter of the depth within 6 to 12 hours.
- Dowels at the street joint, smooth #4 bars greased on one side so panels move together.
None of that is exotic—it is the package a concrete driveway contractor in Austin who builds RV pads quotes as the default, not an upgrade. The Portland Cement Association’s technical library on slab design is a good sanity check.
RV pads and leveling jacks
A dedicated RV pad wants at least 12 by 40 feet, 6 inches thick, graded 1 to 2 percent so water leaves instead of sitting under the tires. If the coach sits on leveling jacks long term, spread those point loads with 12 by 12 inch pads over plywood, or thicken the slab to 8 inches where the jacks land. The apron at the street belongs to the city and carries every heavy vehicle that arrives.
Curing, load time and what the upgrade costs
Summer pours go early, with concrete temperature under about 90°F and evaporation controlled—above 0.2 lb per square foot per hour you need fog spray or a retarder, or you get plastic shrinkage cracks before the crew is off the slab. Then wet cure 7 days. Cars can go on at 7 days; trucks and RVs should wait 28, or for cylinder breaks confirming design strength. I once watched an owner put a motorhome on a 10 day old slab and crack it in an afternoon.
In Austin a plain 4 inch broom-finish driveway runs $8 to $13 per square foot installed; the 6 inch reinforced version over a proper base is $13 to $20. On 700 square feet that is a $3,500 to $5,000 difference—real money, and less than replacing the cheap version once.
Frequently asked questions
Is 4 inches ever enough for a truck? For a light-duty pickup over a well-compacted base, yes. For a loaded three-quarter or one-ton truck, a travel trailer, or anything parked repeatedly near the slab edge, no. Failures show at edges and corners first, which is why edge thickening matters as much as overall depth.
How thick should a concrete RV pad be? Six inches of 4,000 psi concrete with #4 rebar at 18 inches on center, over 6 to 8 inches of compacted base. For a heavy Class A parked year round, 8 inches under the jack and tire areas is cheap insurance.
Will rebar stop the driveway from cracking? No. Concrete on expansive clay cracks somewhere. Rebar and properly spaced control joints decide whether it cracks in a straight sawed line that stays tight, or in a ragged break where the sides step apart and catch tires.