Why Concrete Cracks in Driveways, Walls, Slabs, and More

Concrete is one of the most durable materials used in construction, but it’s not invincible. Over time, cracks can appear in concrete due to various environmental, structural, or installation factors. While some cracking is purely cosmetic, other types signal deeper issues. So why does concrete crack at all?

Knowing what type of structure you’re dealing with—like a driveway, wall, or slab—can help determine the cause of the cracking and whether it’s time for a repair or a full replacement.

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Common Reasons Concrete Cracks

1. Shrinkage Cracks

As concrete cures, it loses moisture and shrinks. If the concrete dries too quickly or is poured without proper control joints, shrinkage cracks can form. These are common in slabs and driveways.

2. Thermal Movement

Concrete expands in the heat and contracts in cold. Without proper expansion joints, this movement can lead to cracking. Outdoor concrete structures like driveways and patios are especially vulnerable.

3. Load Stress

Concrete that isn’t designed for heavy loads may crack under pressure. This is common in garage slabs, commercial flooring, and driveways subjected to frequent or heavy vehicle traffic. See here for load capacities.

4. Subgrade Settlement

If the soil beneath the concrete shifts or settles unevenly, the slab can crack as it tries to adjust. This is particularly problematic in slabs-on-grade and poorly compacted driveways.

5. Improper Installation

Mistakes during mixing, pouring, or finishing—such as too much water in the mix or finishing while water is still bleeding from the surface—can weaken concrete and lead to premature cracking.

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Why Does Concrete Crack In Specific Structures?

🏠 Concrete Driveways

• Common Causes:

  • Freeze-thaw cycles

  • Heavy vehicle loads

  • Poor drainage

  • Inadequate expansion joints

• Typical Cracks:

  • Longitudinal cracks (along the length)

  • Transverse cracks (across the width)

  • Edge cracking due to vehicle weight near borders

• When to Replace:

  • Cracks wider than ¼ inch or with vertical displacement

  • Multiple or spreading cracks

  • Surface scaling or crumbling

  • Areas of significant sinking or heaving

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🧱 Concrete Walls (Foundation or Retaining)

• Common Causes:

  • Soil pressure

  • Hydrostatic pressure (water buildup)

  • Temperature-induced expansion/contraction

  • Poor reinforcement

• Typical Cracks:

  • Vertical or diagonal cracks from settling

  • Horizontal cracks from lateral pressure

  • Stair-step cracks in block foundations

• When to Replace or Reinforce:

  • Cracks wider than ⅛ inch, especially horizontal

  • Signs of bowing or bulging

  • Water leakage

  • Structural instability or exposed rebar

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🏗️ Concrete Slabs (Floors, Basements, Patios)

• Common Causes:

  • Subgrade settlement

  • Overloading

  • Shrinkage and curing issues

  • Inadequate joint placement

• Typical Cracks:

  • Hairline cracks (common but often cosmetic)

  • Wide or uneven cracks from foundation movement

  • Map or spider cracks from surface shrinkage

• When to Replace:

  • Cracks with vertical movement

  • Surface deterioration or spalling

  • Structural issues in basement slabs

  • Persistent moisture problems

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🧱 Concrete Steps and Walkways

• Common Causes:

  • Poor drainage or water pooling

  • Freeze-thaw cycles

  • Inadequate base preparation

• Typical Cracks:

  • Longitudinal or corner cracks

  • Cracking at control joints

• When to Replace:

  • Uneven or crumbling steps (trip hazards)

  • Deep or widening cracks

  • Significant displacement or erosion underneath

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What To Do If Concrete Cracks: Repair or Replace?

Not every crack means your concrete is failing. Many small or superficial cracks can be sealed or patched. But certain signs indicate it’s time to consider replacement:

✅ Cracks wider than ¼ inch
✅ Vertical displacement between sides of a crack
✅ Signs of sinking, bulging, or heaving
✅ Water infiltration through cracks
✅ Corroding or exposed rebar
✅ Deteriorating surface with visible wear or spalling

Pro tip: Always consult a concrete professional or structural engineer if you’re unsure. Early intervention can often save you money and prevent bigger issues down the road. When it comes to foundational structures like concrete, it can end up costing you a lot more if you don’t hire the pros.

Speaking of pros, we are the experts in concrete removal. If you need us to demolish and remove old cracked concrete, we’ve got you.