A driveway in South Hills called me out for what the homeowner described as “the driveway is falling apart,” and what I found was four different cracks that had nothing to do with each other, at four different ages, each telling a different story about what happened underneath. Reading a crack correctly before deciding what to do about it saves real money, because the fix for a crack that opened the night of the pour is nothing like the fix for one that opened five years later over a soft spot in the base.
Plastic shrinkage cracks show up the same day
These are the ones that appear within a few hours of finishing, while the concrete is still curing, usually shallow, short, and running in a random or map-like pattern rather than in a straight line. They come from the surface losing water to evaporation faster than bleed water can replace it, which happens on hot, windy, low-humidity pours more than any other condition. A plastic shrinkage crack is almost always cosmetic and doesn’t run through the slab, but it’s worth checking with a flashlight at a low angle, because on a thin or poorly cured pour it can occasionally go deeper than it looks.
Drying shrinkage cracks arrive over weeks, not hours
Every slab shrinks as it cures and loses moisture over its first month, and that shrinkage has to go somewhere. Where a driveway was cut with control joints at reasonable spacing, the crack you’d otherwise get shows up in the joint instead, hidden in plain sight. Where the joint spacing was too wide, or a joint was skipped, the slab cracks on its own schedule, usually somewhere between two and eight weeks after the pour, in a fairly straight line running roughly perpendicular to the long dimension of the panel. Correct spacing is covered in more detail when I get into how control joints are laid out and how deep they need to be cut, but the short version is that a crack finding the weak point on its own usually means the joints were placed too far apart to begin with.
Structural cracks come with a step you can feel
A structural crack runs the full depth of the slab, and more importantly it usually has a vertical offset between the two sides that you can feel with a foot or measure with a straightedge, rather than just a hairline on the surface. These tend to follow wheel paths or run at an angle out from a corner, and they’re the result of the slab actually failing to carry a load, from inadequate thickness, missing or corroded reinforcement, or a void that opened underneath one side. Any crack with a measurable elevation difference, generally more than about 1/8 inch, is past the point of cosmetic patching and into the category of a real repair decision.
Settlement and frost heave move the ground, not just the concrete
A settlement crack shows up as a localized dip, often tracking a straight line where a utility trench or a poorly compacted patch of backfill sits under the slab, and it tends to keep getting slowly worse rather than stabilizing on its own. Frost heave is different again: in a Kanawha Valley winter running forty to sixty freeze-thaw cycles, a crack caused by heave can actually open wider in cold weather and close back down some in spring, a pattern worth tracking with a tape measure over a season rather than reacting to on the first cold snap. The American Concrete Institute’s guidance on evaluating crack causes, published at concrete.org, is a useful reference for how width and pattern get sorted before anyone settles on a repair method.
Frequently asked questions
What crack width means a driveway needs repair, not just monitoring? As a rough threshold, cracks under about 1/8 inch wide with no vertical offset are usually fine to monitor; wider cracks or any measurable step between the two sides point toward an actual repair.
Can a hairline crack from the day of the pour get worse later? Rarely on its own. A true plastic shrinkage crack is shallow and stays shallow; if a crack that looked cosmetic starts widening or stepping months later, something underneath has changed and it should be reassessed.
Why do cracks in West Virginia driveways open and close with the seasons? Frost heave lifts and drops sections of a slab as ground moisture freezes and thaws through the winter, which can make an existing crack visibly wider in January than it is in July.