Why Houston driveways crack, and what actually prevents it

Drive around this part of Texas and you will see the same cracks in the same places: a diagonal across the corner near the garage, a long crack down the middle of the approach, edges that have dropped away from the slab. That pattern is a soil pattern, not a concrete pattern. Gulf Coast clay is expansive. It takes on water and swells in the wet season, then dries and shrinks in the summer, and it can move a surprising amount doing it. A slab poured straight onto that clay moves with it, and concrete does not bend. What actually helps: A proper base. A compacted base under the slab spreads the load and puts a layer between the concrete and the soil that is doing the moving. Reusing the old base under a new pour is one of the most common shortcuts and one of the most reliable ways to get the same cracks back. Reinforcement that suits the load. Rebar or mesh does not stop concrete cracking. It holds the crack together when it happens, which is the difference between a hairline you ignore and two slabs at different heights. Control joints. Concrete is going to crack. Joints decide where. Cut properly and at the right spacing, the cracks go into the joints where nobody sees them. Drainage. Water running under the edge of a slab is what undermines it. Falls that shed water away from the drive and away from the house, and a culvert that works where the drive meets the ditch, do more for the life of a driveway than an extra inch of concrete. The honest answer on overlays. People often ask whether we can pour over the existing drive. We would rather not. An overlay inherits everything wrong underneath it, and on this soil that is usually a movement problem which comes straight back through the new surface within a few years.