Understanding the Risk of Subsidence

24 October 2022

In prolonged dry weather, parched vegetation saps available water, causing the soil to dry out. Consequently, soil can shrink, and the ground beneath affected buildings may shift. This ground movement is known as subsidence.

While there are many causes of subsidence, hot and dry summers are becoming a common factor. In fact, insurance company LV= saw a 218% increase in subsidence claims across the UK in the first two weeks of August 2022 compared with the same time period in 2021, largely due to summer heatwaves and drought-like conditions.

The frequency of hot and dry summers is expected to increase due to the unprecedented effects of climate change. With such torrid conditions, millions of UK properties may be at heightened risk of subsidence.

If you’re a property owner, it’s crucial to understand the risks of subsidence and check that you have adequate insurance cover. This article outlines subsidence causes, signs of subsidence and related prevention measures.

The frequency of hot and dry summers is increasing due to the unprecedented effects of climate change. With such torrid conditions, millions of UK properties may be at heightened risk of subsidence.

What Causes Subsidence?

The most common cause of subsidence is clay shrinkage; warm weather causes clay-rich soil to shrink as the water trapped within it evaporates. Particularly at risk are a swathe of properties built on clay-rich soils in the southeast of England, the Midlands, the northeast coast and parts of the southwest.

However, warm weather isn’t the only causal factor in subsidence. Other contributors include:

• Poor foundations—Building regulations have changed in recent decades to give modern homes greater resilience from subsiding soils. As such, older properties—particularly those built in the Victorian era—may be at greater risk of subsidence due to shallower foundations. Additionally, poor earth preparation and use of the wrong materials can also lead to foundations shifting beneath a property.  
• Trees—Trees growing near or under a property’s foundation can cause the ground to shift and become less stable. Furthermore, trees can draw the water out of the soil, causing it to shrink.  
• Washing away of soil—Leaking drains, escape of water, flooding and heavy rainfall can wash away soil particles over time. Consequently, the ground can shift or become less stable.

How to Spot Subsidence The damage caused by subsidence can vary from a small inconvenience to a huge structural problem. Regardless, early identification is vital. Look out for the appearance of sudden cracks in the brickwork more than 3 millimetres wide—they’ll usually extend in a diagonal direction and be wider at the top than the bottom. Cracks that extend from the corner of a door or window and become visible internally and externally can also be tell-tale signs. You may also find that windows and doors suddenly start to stick or become difficult to open and shut completely.

If you spot signs of subsidence, it’s important to act quickly; subsidence differs from other perils in that claims can be more complex, involve multiple parties and take longer to settle. Initially, contact your insurance broker so they can arrange an inspection of your property. Be aware that surveyors can decide to monitor a property for up to 12 months before deciding on whether the ground is sinking.

Measures to Prevent Subsidence

Where possible, it’s prudent to take steps to mitigate the impact of—or even prevent—subsidence. Consider these mitigation strategies:

• Be vigilant. By remaining vigilant, you can ensure small issues don’t develop into major crises. If you spot a crack in the wall or have trouble closing windows or doors, take swift action. Although there might be other explanations for such issues, it’s wise to take steps to identify the root cause.
• Ensure home improvements meet building regulations. If you extend or make improvements to your property, the foundation must strictly adhere to current building regulations. This will ensure your property is built to the highest standard.
• Pick trees carefully. Although trees are visually pleasing, remain mindful of the hazards they can present. Planting certain trees (eg those that require large amounts of moisture) could dry out the soil. Before planting trees, determine which soil type your property is built upon. Clay soil is highly porous and can contract more easily than other soils when dry. This may influence your decision on which—if any—trees to plant.
• Hire professionals. If you’re cutting down trees near your property, avoid the temptation to conduct work yourself. Tree removal can create extra moisture in the ground, which may cause soil to shift. As such, engage with professional tree experts first. Additionally, should you suspect subsidence, quickly engage with a professional surveyor to instigate a thorough inspection.

The Importance of Adequate Cover

Having adequate insurance cover is crucial to protect yourself financially from subsidence risks. Although most buildings’ insurance policies cover subsidence, it’s crucial to check the exact cover level because remedial works can be costly in the event of a claim. Additional work may even be necessary first to stabilise the property, and interior redecoration is another cost to factor in.   

Remember to check your policy’s terms in detail. Some policies differ in how they define “main residence”; some will include outbuildings and garages, while others may not. Always check that the cover meets your particular needs.

Conclusion

Subsidence is a growing problem for UK properties, largely due to the frequency of extreme summer temperatures and drought-like conditions. With such parched conditions predicted to occur more frequently due to climate change, subsidence is an issue that all property owners should know how to prevent and recognise.

Moreover, in the event of a claim, policyholders can be left to pay out of pocket if they underestimate the costs involved in remedial works. Therefore, it’s vital to have the correct insurance cover. Make sure you’re properly covered by contacting us today to review your policy.