Structural Cracks: When Should You Worry?

Finding cracks in your home can be alarming. But not all cracks are dangerous - many are simply cosmetic issues caused by normal settling. This guide helps you identify which cracks need immediate attention and which can wait.

Understanding Property Cracks

Cracks appear in UK homes for many reasons. Some are harmless, others indicate serious structural problems. The key is knowing the difference.

Why cracks appear:

In the UK, around 1 in 50 homes experience some form of subsidence or structural movement annually.

Types of Cracks

1. Hairline Cracks

What they are: Fine cracks less than 1mm wide, usually in plaster or render.

Cause: Normal settlement, temperature changes, or minor plaster shrinkage.

Worry level: LOW - Usually cosmetic and easily repaired.

2. Stepped Cracks

What they are: Cracks that follow the mortar lines between bricks in a stepped pattern.

Cause: Structural movement, often subsidence or heave.

Worry level: MEDIUM to HIGH - Needs professional assessment if wider than 5mm.

3. Vertical Cracks

What they are: Straight cracks running up and down walls.

Cause: Settlement in new builds, or structural issues in older properties.

Worry level: MEDIUM - Depends on width and location.

4. Diagonal Cracks

What they are: Cracks running at an angle, often near doors or windows.

Cause: Structural movement, lintel failure, or subsidence.

Worry level: HIGH - Usually indicates ongoing structural problems.

5. Horizontal Cracks

What they are: Cracks running horizontally along walls.

Cause: Pressure from above (roof issues) or lateral pressure.

Worry level: HIGH - Can indicate serious structural instability.

Severity Assessment Guide

Minor Cracks (Less than 1mm)

Moderate Cracks (1-5mm)

Severe Cracks (5-15mm)

Very Severe Cracks (Over 15mm)

Warning Signs of Serious Problems

Seek immediate professional help if you notice:

Location Matters

Internal Cracks

External Cracks

Ceiling Cracks

Common Causes in UK Homes

Subsidence

Ground beneath foundations sinking or washing away.

Signs:

Causes:

Heave

Ground beneath foundations swelling and pushing upward.

Signs:

Causes:

Settlement

Normal compression of ground under weight of building.

Signs:

Causes:

DIY Assessment

How to monitor cracks:

When to Call Professionals

Immediate structural engineer:

Structural survey (within weeks):

Monitor yourself (3-6 months):

Repair Options and Costs

Cosmetic Repairs

Repointing

Crack Stitching

Underpinning

Insurance Considerations

Subsidence cover:

What's usually covered:

Not usually covered:

Prevention Tips

Quick Crack Assessment

Conclusion

Most cracks are harmless, but some indicate serious structural problems. The key is:

Early detection and monitoring can save thousands in repair costs.

This article is for informational purposes only. For structural concerns, always consult a qualified structural engineer or RICS surveyor.