The risk of subsidence in London is rising as extreme heat and prolonged dry conditions cause the clay beneath homes to lose moisture, shrink and shift. During this summer’s blistering temperatures, homeowners across the city began reporting zig-zagging cracks. In addition, sticking doors and warped windows appeared.
London is particularly vulnerable because large parts of the city are built on clay-rich soils. When those soils become saturated, they can absorb water and expand. During prolonged periods of heat and drought, they lose moisture and contract. If that movement occurs unevenly beneath a building’s foundations, the resulting ground movement can cause subsidence.
The problem is not limited to the capital. Building and structural specialists say climate change is expanding the areas of the UK exposed to heat-related subsidence. Moreover, increasingly hot and dry summers are creating conditions in which insurance claims can surge.
The UK’s experience in recent years has provided a clear indication of the financial consequences. In 2025, after an exceptionally hot summer, insurers paid a record $415 million in subsidence-related claims. This was an increase of 10% from the previous year.
The figures have continued to climb. UK insurers paid more than $97 million for subsidence-related claims during the second quarter of 2026. Meanwhile, the average claim reached a record $27,000.
Louise Clark, general insurance policy manager at the Association of British Insurers, said the extremely hot and dry conditions experienced during July and August could lead to further claims in the months ahead.
For homeowners, the concern is not simply cosmetic damage. Subsidence can weaken parts of a building. Furthermore, it can reduce property values, make homes more difficult to sell and create repair bills that can run into tens of thousands of dollars.
Why London Clay Is Vulnerable to Heat-Driven Subsidence
Clay soil behaves differently from many other foundation materials because its volume changes as its moisture content changes. During wet conditions, clay absorbs water and expands. When prolonged heat removes moisture, the soil contracts.
The process is commonly known as “shrink-swell.” Problems arise when the contraction does not occur evenly beneath a property. One section of a foundation may move more than another, putting stress on walls and structural components.
That movement can produce visible warning signs. Cracks may appear around windows and doors or develop in a zig-zag pattern across walls. Doors can become difficult to close, while windows may stick as parts of the building shift relative to one another.
The risk is particularly pronounced in London because some of the city’s clay soils contain expansive minerals that respond strongly to changes in moisture. The capital is also frequently exposed to some of the UK’s highest temperatures.
Trees and vegetation can intensify the process. During hot weather, roots seek additional moisture from the surrounding soil. Additionally, large trees growing close to buildings can draw water from the ground beneath or near foundations. This accelerates the drying and contraction of clay.
UK housing stock data on property age shows why the age of London’s buildings is another important consideration. More than half of the capital’s homes were constructed before 1945. Moreover, older properties can be more vulnerable because they often have shallower foundations.
Climate change adds another layer to that structural vulnerability. Brunella Balzano, a senior lecturer in structural design at Cardiff University in Wales, describes subsidence risk as the interaction between two factors: the vulnerability of the building and the severity of the hazard affecting it.
For heat-driven subsidence, engineers cannot remove the underlying environmental trigger. Instead, interventions have to focus on reducing a building’s vulnerability and limiting the factors that worsen soil movement.
Record Claims Raise Concerns for Homeowners and Insurers
Insurance data illustrates how quickly subsidence can become more expensive during periods of extreme heat and drought.
Association of British Insurers data on subsidence claims shows that the $415 million paid during 2025 represented a record for the industry. The increase followed an unusually hot summer. During that summer, dry conditions placed additional stress on buildings constructed on susceptible soils.
The current year could prove even more difficult. Bob Gibson, director of Building & Structural Consultants, said the combination of another drought summer and multiple heatwaves could make 2026 the biggest year for subsidence claims on record.
The financial impact is already being reflected in individual claims. The average UK subsidence claim reached $27,000 in the second quarter of 2026. This was more than $2,700 higher than during the same period a year earlier.
UK Met Office climate data recorded the extraordinary heat experienced during the previous summer. This provides additional context for why insurers and structural specialists are watching the relationship between temperature, drought and property damage.
Aviva has also reported an increase in subsidence claims during 2026. The insurer has warned that the trend could continue unless significant rainfall restores moisture to the ground.
That creates a difficult situation for homeowners in areas where the risk is already high. Aviva data projects that by 2030, possible or probable subsidence risk could affect 100% of properties in some parts of London. These include central areas such as Kensington, the City of London and Westminster.
The longer-term outlook is even more concerning. British Geological Survey data indicates that more than 26% of properties in London could be affected by subsidence by 2070. This would occur if global warming continues at approximately its current pace.
The growing risk could also affect the availability and cost of insurance. Gibson said some homeowners in high-risk areas are already facing substantially higher premiums or difficulties renewing subsidence cover.
That creates an additional dilemma. Homeowners may become reluctant to report early signs of damage if they fear higher premiums or losing coverage. Yet delaying investigation can allow a structural problem to become more difficult and expensive to address.
For insurers, the challenge is equally significant. Subsidence can develop gradually and may require lengthy investigations and repairs. If climate-driven claims continue increasing, insurers could reassess how much of that risk they are prepared to accept.
Balzano has warned that subsidence could potentially become more difficult to insure in the future if the underlying climate risk continues to intensify.
How Homeowners Can Respond to Growing Subsidence Risk
There is no single solution to heat-driven subsidence because the underlying hazard is linked to soil moisture and increasingly extreme weather. Engineers therefore focus on measures that reduce pressure on vulnerable foundations.
One approach is managing nearby vegetation. Removing trees or other plants can reduce the amount of water extracted from the soil. In some circumstances, barriers can also be installed to prevent roots from reaching areas immediately beneath or around a building’s foundations.
More extensive damage may require underpinning. This involves strengthening or extending the foundation system, potentially by installing structural support beneath the existing foundations. It can be an expensive and disruptive intervention, making early assessment particularly important.
Not every crack indicates subsidence. Buildings can develop cracks for many reasons, including normal movement and changes in materials. However, rapidly developing or distinctive cracking, especially when accompanied by sticking doors or windows, can warrant professional investigation.
The broader challenge is that the UK’s building stock was not designed for the frequency and intensity of some of the weather conditions now being experienced. The interaction between older buildings, clay soils, vegetation and prolonged heat creates a risk. This risk becomes more significant when dry summers occur repeatedly.
The British Geological Survey has highlighted the scale of the potential exposure across millions of UK homes. Climate-related changes in soil moisture are expected to remain an important consideration for subsidence risk.
For homeowners, that makes property maintenance and early detection increasingly important. For insurers, it raises difficult questions about how much climate-related structural risk can remain affordable to cover.
Subsidence is rarely an immediate threat to life. It is generally less dramatic than a flood destroying a home, a wildfire consuming a property or coastal erosion taking land away. Yet its effects can accumulate slowly. As a result, homeowners are left with structural damage, falling property values and substantial repair costs.
As hot and dry summers become more frequent, the cracks appearing in London’s buildings are becoming another visible expression. They show how climate change is altering everyday risks for people and the properties they depend on.
