The UK is experiencing a surge in subsidence claims as a result of the hottest summer on record, with experts warning that payouts may rise even higher this year amid forecasts of El Niño weather patterns. Repeated heatwaves over the past two years have caused shrinkage and sinking in clay soils beneath homes, leading to cracking walls, uneven floors, and doors or windows that no longer fit their frames. This phenomenon, driven by soil moisture loss, has placed widespread pressure on properties, particularly older ones with shallow foundations.

One homeowner in northwest London recently woke to the sound of severe cracking in her Victorian house, which had undergone previous underpinning for subsidence. The damage this time involved bricks splitting apart, rendering the house unsafe to occupy. Ground engineering specialists from Mainmark UK are managing the case, highlighting both the severity and speed at which damage is occurring.

Building professionals report a consistent rise in calls from homeowners, especially those living in pre-1930 properties or buildings altered through extensions or amalgamations, which tend to exacerbate subsidence-related problems. Insurers have classified 2022, 2025, and 2026 as “surge events,” with more than 50,000 claims filed each year. The Association of British Insurers (ABI) estimates payouts at £219 million following the 2022 heatwave and £307 million in 2025, reflecting an 89 percent increase in subsidence payouts over three years. The average claim cost has also more than doubled since 2017, reaching about £17,000 in 2025.

The potential impact of El Niño could intensify these issues as wetter autumn and winter conditions bring cycles of soil shrinkage followed by expansion, known as heave, increasing structural stress. However, some experts caution that the “autumn reset”—when rainfall replenishes soil moisture—is yet to take place, leaving soil abnormally dry and trees more likely to extend their roots in search of moisture, further destabilizing foundations.

Subsidence hotspots are concentrated in London and the South East, where clay-rich soils prevail, especially in boroughs like Camden, Islington, Barnet, Kensington and Chelsea, Westminster, and Lambeth. Other regions, including East Anglia, East Midlands, and parts of Yorkshire, are also seeing rising claim numbers. The British Geological Survey (BGS) projects that under medium-carbon emissions scenarios, approximately 5 percent of UK properties could be highly susceptible to shrink-swell clay subsidence within four decades, rising to 11 percent under higher emissions. In London, this risk is more pronounced, with up to 26 percent of homes vulnerable under medium scenarios, reaching 54 percent under high emissions.

The subsidence problem is creating challenges for homeowners, mortgage lenders, and insurers alike. Properties that have undergone subsidence repairs may suffer residual value reductions of 5-10 percent, while those with active movement can face market discounts exceeding 20 percent. Leasehold buyers should be particularly vigilant, as they may be liable for repair costs to common parts of buildings even if their individual units show no damage.

Insurance companies have reclassified many properties on shrink-swell clay as “high risk,” increasing premiums or excesses and imposing more stringent survey requirements. This shift has raised concerns about homes becoming uninsurable or unmortgageable, although some specialists argue subsidence risk remains unpredictable at the individual level, making widespread uninsurability unlikely.

Traditional underpinning remains the primary method of subsidence remediation, involving controlled excavation beneath existing foundations and concrete reinforcement, with costs typically ranging from £1,500 to £3,000 per linear metre. However, some engineers warn partial underpinning can worsen structural movement if different sections shift independently. Alternative techniques gaining popularity include screw piling, which is less disruptive and faster, and innovative precision lifting technologies such as computer-controlled grouting systems that rebalance buildings gradually.

Geopolymer resin injection, pioneered by companies like Geobear, offers another less invasive, cost-effective method. This process involves injecting engineered materials into weak ground to stabilize soil and fill voids, often completed within a day compared to weeks for underpinning.

Mature trees with extensive root systems can exacerbate subsidence on clay soils by increasing seasonal drying through moisture uptake. In such cases, solutions like copper geotextile root barriers can redirect roots away from foundations as an alternative to tree removal, which risks destabilizing the soil further.

Despite the rising prevalence and costs of subsidence damage, many homeowners remain underinsured. Experts emphasize the importance of accurately calculating rebuild costs—distinct from market value—especially after home extensions or improvements, noting that underinsurance can result in reduced claim payouts. Meanwhile, some property owners opt to address minor cracking independently rather than filing insurance claims, seeking to avoid the stigma that subsidence history can impart on property values and mortgage applications.

Industry bodies advise homeowners to monitor cracks carefully, particularly if a gap widens beyond 3mm or shows signs of expanding, recommending professional surveys over immediate cosmetic repairs. With subsidence-related damage continuing to evolve rapidly, specialists stress the need for early intervention and thorough insurance coverage in managing the growing risks to Britain’s housing stock.