Subsidence: What Homeowners Need to Know

Cracks appearing in your home can be worrying, but not every crack is a sign of subsidence. Buildings naturally move over time due to changes in temperature, moisture levels and the ageing of materials. Understanding the signs of subsidence and knowing when to seek professional advice can help you take the right action and avoid unnecessary concern.

Subsidence occurs when the ground beneath a building sinks or moves, causing foundations to shift and potentially resulting in cracking, distortion and, in severe cases, structural damage.

Common causes of subsidence include:

• Clay soils shrinking during prolonged dry weather
• Tree roots extracting moisture from the ground
• Leaking drains washing away supporting soil
• Ground instability or historic mining activity
• Poorly compacted ground beneath foundations

How to Spot Potential Subsidence

While many cracks are harmless, certain patterns of movement may indicate a more significant structural issue. If you are concerned about possible subsidence, there are several warning signs to watch for.

• Cracks in walls, particularly diagonal cracks around doors and windows, cracks that are wider at one end than the other, cracks that pass through bricks and mortar rather than just plaster, or cracks wider than 3mm that appear to be growing.
• Doors and Windows Sticking, structural movement can cause door and window frames to distort, making them difficult to open or close.
• Uneven Floors, floors may begin to slope or feel uneven where movement has occurred.
• External signs of movement can include cracks in external brickwork, gaps appearing around doors, windows or pipework, separation between an extension and the original property, or walls and other structures that appear to be leaning or distorted.

Finding a crack does not necessarily mean your home is suffering from subsidence.

A sensible first step is to monitor any movement by:

• Taking clear photographs
• Measuring crack widths
• Recording dates
• Checking periodically for changes

If cracks remain stable over time, they may simply reflect normal seasonal movement or settlement. However, if cracks continue to widen, new cracks appear, or other signs of movement develop, professional advice should be sought from a structural engineer, building surveyor or your insurer.

The appropriate solution depends on the underlying cause. In some cases, repairing a leaking drain or managing nearby vegetation may prevent further movement. More significant cases may require structural repairs or underpinning to strengthen the foundations.

Before any remedial work is undertaken, it is important to identify the cause of the movement. Your insurer, structural engineer or surveyor can help determine the most appropriate course of action.

What can be done about Subsidence?

The appropriate solution depends on the underlying cause. Possible solutions may include:

• Repairing drains where leaking pipework has washed away or weakened the soil supporting the foundations.
• Managing trees and vegetation where roots may be contributing to ground movement by extracting moisture from the soil.
• Underpinning foundations to provide support from more stable ground. Underpinning is a significant structural alteration and will generally require Building Regulations approval.
• Carrying out structural repairs once the cause of the movement has been addressed and the building has stabilised.

Does Hot Weather Cause Subsidence?

Extended periods of hot, dry weather can cause clay soils to shrink as moisture evaporates from the ground. This can increase the risk of movement beneath foundations, particularly where large trees or shrubs are present.

In recent years, periods of prolonged dry weather have resulted in increased reports of cracking and movement across many parts of Surrey and the South East. Properties founded on shrinkable clay soils are generally more susceptible to movement during prolonged dry periods.

Can Tree Roots Cause Subsidence?

In some circumstances, yes.

Trees and large shrubs can remove significant amounts of water from clay soils, causing the ground to shrink. However, tree removal is not always the answer. In some circumstances, removing a mature tree can cause the ground to swell and create different structural problems.

Professional arboricultural and structural advice should always be sought before undertaking significant tree work.

Building Control and Building Regulations

Monitoring cracks or carrying out investigations into possible subsidence does not usually require Building Regulations approval.

However, approval is typically required where structural works are undertaken to address subsidence, including:

• Underpinning foundations
• Structural strengthening
• Rebuilding structural walls
• Installing structural supports or beams

Building Regulations approval helps ensure these works are designed and carried out safely and in accordance with current standards.

If you are unsure whether your project requires approval, contact Southern Building Control Partnership before work starts.

Useful guidance – Building Regulations and Underpinning 

Can I Claim on My Insurance?

Many home insurance policies include cover for subsidence, subject to the terms and conditions of the policy. If you believe your property may be affected:

• Contact your insurer as soon as possible.
• Follow their claims process.
• Cooperate with any investigations they arrange.

Your insurer may appoint a loss adjuster, structural engineer or specialist surveyor to determine the cause of the movement and recommend remedial action.

It is important to note that Building Control does not assess insurance claims or determine whether subsidence is covered by your policy. Any questions regarding policy coverage, excesses or claims should be directed to your insurance provider.

What If I’m Worried About a Building That Isn’t Mine?

Most cases of subsidence develop gradually, but occasionally structural movement can result in a building becoming dangerous. You should report concerns if you notice:

• Walls leaning or bulging significantly
• Loose masonry
• A chimney that appears unstable
• Severe structural cracking
• Signs that part of a structure could collapse

If there is an immediate risk to public safety, stay away from the area and contact the emergency services.

For non-emergency concerns regarding potentially dangerous structures, contact Southern Building Control Partnership through our Dangerous Structures reporting service.

If you are concerned about cracks or structural movement in your property, seek professional advice early. While many cracks are harmless, monitoring and investigation can help identify more serious issues before they become costly to repair.

Does every crack mean my house has subsidence?

No. Most cracks are caused by normal building movement, thermal expansion and contraction, drying plaster, or minor settlement.

Are older houses more likely to suffer from subsidence?

Not necessarily. While older buildings may display more visible cracking, many have already undergone decades of settlement and stabilisation.

How long should cracks be monitored?

This varies depending on the circumstances, but monitoring often takes several months to establish whether movement is ongoing, historic, or simply seasonal.

Can subsidence stop on its own?

Sometimes. If the cause is identified and removed, such as repairing a leaking drain, movement may stabilise. Professional advice should always be sought before assuming the issue has been resolved.

Useful Resources

LABC Front Door: Subsidence, Movement and Your Conservatory
LABC Front Door: Do I Need Building Regulations Approval for Underpinning?