Which cracks actually matter
Every concrete surface gets fine hairline cracks as it cures and ages, and those are cosmetic and can be sealed. The ones that matter are wide cracks, cracks where one side is higher than the other, and cracks that keep growing, because those say the base under the slab moved or failed. A good crew reads the crack to tell you whether you have a surface issue or a foundation issue, and those are very different bills.
When it is the ground, not the concrete
Concrete that is settling on one side, heaving up, or cracking in a spreading pattern usually has a problem underneath, the expansive clay soil moving or water washing out the base, and patching the top does nothing if the cause is below. On this coast that soil movement is the usual suspect. A repair that ignores the base is a patch that fails again, so the honest fix sometimes means addressing the ground or, if it is bad enough, replacing the slab.
Repair or replace, honestly
A sound slab with surface damage is worth repairing. A slab that is broken up, badly settled, or cracked through from a failed base is often cheaper to tear out and pour right than to keep patching, and a straight crew will tell you when you have crossed that line instead of selling you repair after repair. The tell is whether the underlying base can be fixed or whether the slab itself is compromised.
- Hairline cracks are normal; wide or offset cracks are not
- Settling and heaving point to a base or soil problem
- Sometimes a repair is throwing money at a slab that is done
