Subsidence cracks are caused by movement in the ground beneath a building’s foundations. When the soil shrinks, shifts or becomes unstable, part of the property can drop slightly, leading to visible cracking in walls and brickwork.

While not all cracks indicate subsidence, certain patterns and symptoms should not be ignored.

What Do Subsidence Cracks Look Like?

Subsidence cracks often:

• Run diagonally across walls
• Follow a stair-step pattern in brickwork
• Are wider at one end
• Appear around windows and doors
• Extend from floor level upwards
• Are visible both internally and externally

Cracks caused by subsidence usually affect masonry rather than just plaster.

Common Causes of Subsidence

Subsidence can be triggered by:

• Clay soil shrinking during dry weather
• Large trees drawing moisture from the ground
• Damaged drains washing away soil
• Poor ground compaction
• Historic mining or ground instability

Seasonal movement is common in clay-heavy areas.

Warning Signs That May Indicate Subsidence

Cracks may be linked to subsidence if you also notice:

• Doors and windows sticking
• Sloping or uneven floors
• Gaps between walls and ceilings
• Cracks reappearing after repair
• Exterior brickwork bulging
• Cracks that widen over time

The combination of symptoms is more important than one small crack alone.

When Should You Be Concerned?

You should consider further investigation if:

• Cracks exceed 5mm
• Multiple cracks appear suddenly
• The crack widens noticeably over months
• There are signs of foundation movement externally

Monitoring crack progression is essential before drawing conclusions.

How to Monitor Potential Subsidence Cracks

• Measure and record crack width.
• Mark the ends and date them.
• Take photographs every few months.
• Check during both wet and dry seasons.
• Inspect the same location externally.

If cracks continue to widen or additional symptoms appear, professional assessment may be required.

Final Thoughts

Most wall cracks are not caused by subsidence. However, diagonal or stair-step cracks that widen over time — particularly when combined with sticking doors or sloping floors — may indicate ground movement. Identifying the signs early allows for proper investigation before cosmetic repairs are carried out.

Addressing the cause, rather than simply filling the crack, prevents recurring structural damage.