Why Does Concrete Crack? (Is It Normal?)

Why Concrete Cracks: Normal vs Problematic

All concrete cracks. This is a fact, not a defect. The question is whether the cracks are normal (controlled) or indicate a problem. This guide explains the difference and when to worry.

Why All Concrete Cracks

Concrete cracks due to:

• Shrinkage: Concrete shrinks as it cures and dries
• Temperature changes: Expansion and contraction
• Tensile stress: Concrete is strong in compression but weak in tension

These forces are inevitable. The goal isn't to prevent cracking—it's to control where cracks occur.

Control Joints: Guiding Cracks

Control joints are intentional cuts or grooves that weaken the concrete at specific locations. When the concrete cracks (and it will), it cracks in the joint where it's supposed to.

Think of it like: Perforated paper—it tears where you want it to tear.

Normal Cracks vs Problem Cracks

Normal cracks (in control joints):

• Hairline to 1/8 inch wide
• Located in control joints
• Straight, uniform
• Cosmetic only

Problem cracks (structural issues):

• Wider than a credit card (approximately 1/8 inch)
• Not in control joints
• Uneven, jagged
• Indicate foundation or base failure

When to Worry

Worry if cracks are:

• Wider than a credit card
• Getting wider over time
• Not in control joints
• Accompanied by settling or heaving

These indicate structural problems that need professional assessment and repair.

The Bottom Line

All concrete cracks—it's normal. Control joints guide cracks to the right places. Hairline cracks in joints are cosmetic and expected. Cracks wider than a credit card or outside joints indicate problems that need attention.

Don't panic about normal cracking. But do address structural cracks promptly to prevent further damage.