Subsidence is damage caused when the ground beneath a building shrinks or shifts, cracking the foundations. In the UK it is driven mainly by clay soils that dry out in long hot spells, then swell again when rain returns. As summers grow hotter and drier, subsidence claims are becoming more common and more expensive, and that cost feeds into home premiums across the south and east where clay is widespread.
What causes it
Most UK subsidence starts with moisture. Clay-rich soil shrinks as it dries, pulling foundations down on one side more than another. The usual triggers are:
- Prolonged dry, hot weather that bakes the soil.
- Mature trees and shrubs drawing water from the ground near the walls.
- Poor drainage or leaking drains that wash or soften the soil.
- Old or shallow foundations that cannot ride out the movement.
The damage shows as diagonal cracks, often near doors and windows, that widen in dry months and narrow when wet returns. Our analysis of home insurance claims data records subsidence as one of the costliest single home claims, with an average well into five figures.
How it is covered
Standard buildings insurance includes subsidence, but it is one of the most investigated claims because the cause must be clear and the fix can be long. The insurer will usually appoint a surveyor to monitor movement over a dry season before committing to works. Cover excludes the cost of preventive tree management you should have done, and it excludes gradual settlement that is not a single identifiable event.
Expect an excess that is higher than your standard one, because subsidence claims are expensive to assess and repair. The claim can stay open for months while the property is monitored, which is normal rather than a sign of delay. Our guide to how insurance settlements and payouts work explains how a complex claim is handled.
Why climate makes it worse
A warming climate lengthens the dry spells that drive clay shrinkage. More properties cross the threshold from “stable” to “moving” in a single hot summer, and claims cluster in the same regions year after year. The Association of British Insurers tracks this as part of weather-related claims, and the rising average cost is one reason home premiums move even when storm and flood do not.
Insurers price subsidence by location and soil type, so two nearby streets can differ sharply. The Financial Conduct Authority expects that loading to be fair and explained, and the Consumer Duty reinforces that vulnerable customers should not be priced out without reason.
What you can do
- Keep trees and large shrubs a safe distance from the building, sized to the soil.
- Fix leaking drains promptly, because water is as damaging as drought.
- Manage drainage so water does not pool against the walls.
- Act early if you see new cracks, because monitoring limits the damage.
Good maintenance is cheaper than a claim, and it reduces the risk loading on your renewal. Read how insurers calculate risk and price cover to see how these factors enter your premium.
Sources
- Insurers — how subsidence risk is assessed.
- Financial Conduct Authority (FCA) — fair pricing and climate risk.
- Association of British Insurers (ABI) — subsidence and weather claims data.
- Existing analysis: home insurance claims data.