British Geological Survey warns of rising subsidence risk in London

In the first half of 2025, UK insurers paid £153 million in subsidence-related claims after the country recorded its warmest spring on record and its driest spring in more than 50 years. The Guardian reports that a new British Geological Survey (BGS) analysis now flags millions of homes in London and parts of the south-east as vulnerable as hotter, drier summers make clay-rich ground shrink and pull at foundations.

The mechanism is old, but the risk map is shifting with the weather. BGS scientists combined geotechnical data with projected rainfall and temperature scenarios to identify where “shrink-swell” subsidence is most likely across Great Britain, according to the Guardian. London stands out because it is expected to see larger changes in rainfall and temperature and because its density of buildings turns marginal ground movement into a mass property problem. What looks like a climate story quickly becomes a balance-sheet story: subsidence can slash a home’s value, and lenders often refuse mortgages until the issue is remediated.

The remediation is rarely cheap or quick. The Guardian notes that mitigation can include land stabilisation, underpinning, replacing utility pipes, or removing trees and vegetation that worsen soil drying. Those are engineering jobs paid for house by house, typically after damage appears—diagonal cracks around doors and windows, sloping floors—rather than as a coordinated infrastructure programme. The result is a system where the costs arrive as individual shocks, but the drivers are regional and cumulative.

BGS projections push the problem from anecdote to planning horizon. By 2070, under a low-emissions scenario aligned with the Paris Agreement, around 500,000 properties could be affected by shrink-swell subsidence, the Guardian reports. Under a medium-emissions scenario closer to current trajectories, the number rises to more than 1.8 million. For London specifically, the Guardian cites an estimate that over 26% of properties could be affected under the medium scenario, with boroughs including Camden, Islington and Barnet among the most susceptible.

The second-order effects are already visible in how risk is priced. Insurance claims translate into higher premiums and tighter underwriting; mortgage refusals can freeze transactions; and repairs can push costs onto homeowners who did not choose the soil beneath their houses. Local authorities can influence trees, drainage and planning rules, but the liabilities are fragmented across private owners, insurers and utilities, leaving no single actor responsible for reducing the aggregate exposure.

The BGS analysis identifies a broad vulnerable band from Oxford up to the Wash, but London’s concentration of older housing stock means small ground shifts can become a citywide finance problem. The cracks start in plaster, and then they show up in the mortgage application.