Londoners find ‘horrendous’ cracks in their homes after successive heat waves

Record subsidence claims after heatwaves dry out London's clay soil

Londoners are facing historic levels of subsidence risk after five successive heatwaves dried out the clay soil on which much of the city is built, reported by the South China Morning Post and The Philadelphia Inquirer. Insurance claims tied to subsidence — a phenomenon where hot, dry weather shrinks the soil and destabilizes building foundations — hit a record last quarter, according to data provided by the Association of British Insurers (ABI). On average, households claimed £20,000 ($27,200) for damage, more than in any previous quarter and a 15% jump from the same period in 2025.

Laura Hughes, head of general insurance at the ABI, said the upward trend is likely to continue. "We expect to see more subsidence cases because of the hot weather," she said in an interview. Hughes also warned, as reported by NZ Herald, "The impact that climate change is having is undeniable."

Homeowners share 'horrendous' experiences

Londoners have taken to social media to express their dismay. On Reddit, people offered personal accounts of "horrendous cracking" in their homes and "doors sticking" due to subsidence. One said it was "genuinely scary" to discover that their kitchen had moved as the foundations of the home shifted. Another Reddit user described the response of a structural engineer they contacted for help: "Before I could finish explaining he laughed and said, 'You and 20,000 other people in southeast London'."

Otso Lahtinen, chief executive of Geobear, an engineering firm called in to repair subsidence damage, said, "It's crazy, what's happening now. It's the new norm, and it seems it will happen more often in the next 20-30 years." He later added, as reported by The Philadelphia Inquirer and NZ Herald, "It's a pretty severe situation. If you're looking to trade, sell or buy property, this is a trend you can't ignore."

Where subsidence hits hardest

Data provided by Aviva show that the areas of London most at risk are some of the UK capital's most sought-after: the boroughs of Westminster, Kensington, and Chelsea. While subsidence has affected London homes for decades, climate change is making it worse. London clay is especially sensitive to moisture fluctuations, expanding when wet and contracting when dry.

The most vulnerable properties are Victorian and Edwardian homes built directly onto the upper layers of London clay. By contrast, modern office buildings in the City of London and Canary Wharf have deeper foundations and are less exposed to such risks. Geobear says it received more homeowner inquiries this summer than ever before, and one insurance client received 180 claims on a single day.

Insurance payouts for subsidence damage in the UK soared roughly 90% in the four years through 2025 to reach a record £297 million, according to data provided by the ABI. The threat is concentrated in and around London and parts of the southeast.

The cost of fixing the damage

Subsidence comes with a hefty price tag. The traditional engineering fix, known as underpinning, can cost anywhere from £20,000 to more than £100,000. Property values also take a hit: the Federation of Master Builders estimates subsidence can devalue a home by 20-25%, a detail reported by The Philadelphia Inquirer and NZ Herald.

Cherry Chan, a partner at Deloitte, said the phenomenon poses "a significant challenge for UK home insurers." The consultancy warned that UK home insurers risk losses in 2026 due in part to the trend, as reported by both The Philadelphia Inquirer and NZ Herald.

Wider heat pressures and climate projections

The wider context of heat-related challenges to adapt is stark. Over recent months, extreme heat has forced schools to close, led bus drivers to go on strike, and seen banks relax in-office requirements to protect staff from unbearably hot commutes. Most of England has been gripped by drought, and the country's hospitals have shown signs of buckling under the strain.

London Mayor Sadiq Khan has warned the city must turn to private investors to help cope with rising temperatures. His office estimates that London faces an annual bill as high as £36 billion into the 2050s to prepare for what climate change has in store.

Looking ahead, estimates from the British Geological Survey indicate that under moderate emissions scenarios, 1.8 million UK properties (about 5% of the total) could be susceptible to shrink-swell subsidence by 2070. Under a higher emissions scenario, that figure rises to 4.2 million properties, or 11% of the UK total.

Perspectives

Homeowners: Residents describe emotional strain and financial burden with their homes. A Reddit user said discovering a shifted kitchen was "genuinely scary" and another described being told by a structural company that they were one of "20,000 people in southeast London" with the same problem.

Engineering industry: Otso Lahtinen was deeply concerned about the trend's direction, calling it a "new norm" and saying the situation is "pretty severe" for the property market.

Insurance sector: Laura Hughes of the ABI expects subsidence insurance claims to grow as heat waves, and Deloitte's Cherry Chan warns of significant losses in 2026.

Local authorities: London Mayor Sadiq Khan's office stresses the long-term financial scale of climate risk—£36 billion annually into the 2050s—and argues for private investment.

Scientific community: Figures from the British Geological Survey underline how climate scenarios would amplify the number of susceptible properties, emphasizing the urgency of the issue.