Homeowner diagnosis guide
Signs of Bad Concrete — and What Each One Means
Not every crack means you need to tear out the driveway — and not every smooth surface is sound underneath. Here's how to read the seven most common signs of failing concrete: what each looks like, why it happened, whether it's cosmetic or structural, and how it typically gets fixed.
Local climate drives a lot of this — de-icing salt and freeze-thaw in the North, expansive clay and heat in the South. Your city's contractor page covers the conditions specific to where you live.
Scaling & spalling
Starts cosmetic, turns structural as it deepens- What you see:
- The top surface flakes, peels, or chips away, exposing the aggregate underneath.
- Why it happens:
- Freeze-thaw damage — made worse by de-icing salt, a mix with no air-entrainment, or a surface that was over-troweled or had water worked into it during finishing.
- Typical fix:
- A resurfacing overlay if it's shallow; full replacement once it's deep.
Sunken / settled slab
Structural — and a trip hazard- What you see:
- One section has dropped below the rest, leaving a lip at the joints.
- Why it happens:
- The sub-base was never properly compacted, fill washed out, or poor drainage eroded voids beneath the slab.
- Typical fix:
- Mudjacking or polyjacking can lift an intact slab for far less than replacement; replace it if it's also cracked through.
Wide or offset cracks
Structural- What you see:
- Cracks you could fit a coin into, or where one side sits higher than the other.
- Why it happens:
- Missing or undersized reinforcement, no control joints, a slab poured too thin, or the base moving underneath.
- Typical fix:
- Sealing buys time on hairlines, but wide or offset cracks usually mean section or full replacement.
Crazing (spider-web cracks)
Cosmetic in most cases (surface only)- What you see:
- A network of fine, shallow surface cracks, like the pattern in dried mud.
- Why it happens:
- The surface dried too fast — a hot day, wind, or no curing — so the very top layer crazed.
- Typical fix:
- Often just sealing; resurface if you want it gone visually.
Pop-outs
Cosmetic unless widespread- What you see:
- Small cone-shaped craters where a chunk has blown out of the surface.
- Why it happens:
- A porous or reactive piece of aggregate near the surface absorbed water and burst during a freeze.
- Typical fix:
- Patch the craters and monitor; widespread pop-outs point to a bad aggregate batch.
Heaving
Structural — and a trip hazard- What you see:
- A slab pushed upward — the opposite of settling — often lifting at a joint or edge.
- Why it happens:
- Frost heave (water under the slab freezes and expands) or tree-root pressure from below.
- Typical fix:
- Fix the water or root cause first, then replace the affected sections.
Efflorescence & discoloration
Cosmetic, but a signal to check drainage- What you see:
- White chalky deposits or blotchy color bleeding through the surface.
- Why it happens:
- Moisture wicking soluble salts up through the concrete — usually a drainage tell, not a strength problem.
- Typical fix:
- Clean the deposits and correct the moisture source so it doesn't return.
Not sure how bad yours is?
A good local contractor will tell you honestly whether you're looking at a seal, a resurface, or a replacement — and the price gap between them is huge. Get free assessments from up to three vetted concrete pros in your area.