Full Breakdown
London Faces Record Subsidence Claims as Heatwaves Dry Out Clay Foundations
8/24/2026, 9:44:12 PM
Record Claims and Rising Payouts
Five successive heatwaves this summer have driven a surge in subsidence-related insurance claims across London. The Association of British Insurers (ABI) reports that the last quarter saw a record average household claim of £20,000, a 15 % increase over the same period in 2025. Over the four years through 2025, ABI data show insurance payouts for subsidence damage rose roughly 90 % to a total of £297 million.
Clay Soil, Climate Change, and Vulnerable Housing
London’s historic clay substrate expands when wet and contracts during dry spells, making foundations especially prone to shrink-swell movement. Victorian and Edwardian homes built directly on the upper layers of this clay are the most exposed, whereas modern office towers in the City and Canary Wharf have deeper foundations and face lower risk. The British Geological Survey estimates that, under the RCP 4.5 emissions scenario, 1.8 million UK properties (about 5 % of the national stock) will be “highly likely or extremely likely” to experience subsidence by 2070; the figure could rise to 4.2 million (11 %) under a higher-emissions pathway.
Financial and Market Consequences
The Federation of Master Builders notes that subsidence can reduce a property’s value by 20-25 %. Repair methods such as underpinning can cost between £20,000 and over £100,000. Cherry Chan, a partner at Deloitte, warns that subsidence claims are becoming an “increasingly material climate-related risk” for insurers, potentially leading to higher premiums and strained loss reserves in 2026.
Official Responses
London Mayor Sadiq Khan has cautioned that the city may need to attract private investment to fund climate-adaptation measures, estimating an annual cost of up to £36 billion into the 2050s. Laura Hughes, head of general insurance at the ABI, emphasizes that “the impact that climate change is having is undeniable.”
Verbatim Quotes
- “The impact that climate change is having is undeniable,” — Laura Hughes
