Why Concrete Cracks (And When It’s a Problem)

Concrete cracking is one of the most common concerns homeowners raise — and not all cracks mean failure.

Understanding why concrete cracks and when it’s serious helps you avoid unnecessary panic or, worse, ignoring a real problem.

Shrinkage vs Structural Cracks

Shrinkage cracks

• Thin, hairline cracks

• Usually appear soon after pouring

• Caused by moisture loss during curing

• Often cosmetic only

  
  

Structural cracks

• Wider, deeper, or uneven

• May continue growing over time

• Can indicate movement or poor reinforcement

• Often require professional assessment

  
  

Poor Reinforcement Placement

Concrete relies on reinforcement for strength.

Common issues:

• Mesh placed directly on the ground

• Reinforcement not tied or supported

• Incorrect spacing or cover

  
  

When steel is in the wrong position, cracks are almost inevitable.

Ground Movement

Movement beneath the slab is a major contributor to cracking:

• Reactive clay soils

• Poorly compacted fill

• Water ingress softening the base

  
  

How CWG NSW Prevents Cracking

✔ Proper base preparation and compaction

✔ Correct reinforcement placement and support

✔ Controlled pouring and finishing

✔ Proper curing procedures

Concrete will crack — uncontrolled cracking is what we prevent.