Why Concrete Driveways Crack in Year Two

Here's the sequence: the ground under the slab wasn't compacted, so it settles unevenly. Water works into the low spots, freezes, and heaves. Now the slab is a bridge over voids, flexing every time a vehicle rolls across. Concrete is enormously strong in compression and weak in bending — so it cracks right over the soft spot.

By the time you see the crack, the cause has been down there since before the pour.

Three things, in order of importance. First, a deeply compacted subgrade — we spend the entire first day of a driveway job on excavation and compaction, before any concrete is ordered. Second, rebar in the slab, which holds a crack tight if one ever forms and keeps the panels acting as one piece. Third, control joints cut on schedule, which give shrinkage cracks a straight, planned place to happen instead of a random one.

None of those three are visible in the finished driveway. All three are why it still looks right in year ten.

A higher-strength mix poured over the same soft ground still cracks — it just costs more first. Sealers protect the surface from salt; they do nothing for the base. And a thicker slab over uncompacted fill is a heavier bridge over the same voids.

If you're comparing bids, ask each contractor one question: what happens before the concrete truck comes? The answer tells you whose driveway cracks in year two.