Data sources current as of July 2026
The UK subsidence risk postcode checker is free and covers 1.8 million postcodes. Enter any postcode above for an instant area-level subsidence risk rating, drawn from British Geological Survey GeoClimate shrink-swell data. Try example postcodes like SE16 4TL (Rotherhithe), SW18 1TU (Wandsworth) or CO1 2ZT (Colchester) to see High subsidence-band results, or enter any UK postcode above. Coverage spans England, Wales and Scotland. Around 4.5 million UK homes sit in areas with some level of clay shrink-swell exposure, concentrated in London, the South East, the Thames Valley and parts of the Midlands. The guide below covers what subsidence is, how to read the band returned for your postcode, what to do if you spot cracks, and how shrink-swell risk affects buying decisions, insurance premiums and claim costs.
| LocalRisk band | BGS shrink-swell potential |
|---|---|
| Lower | Low clay shrink-swell potential |
| Medium | Moderate shrink-swell potential |
| Higher | High shrink-swell potential (clay-rich ground) |
Most UK subsidence stems from clay shrink-swell. Clay-rich soils expand when wet and contract when dry, and this volume change puts pressure on foundations. Hot, dry summers speed the process up. Trees planted close to buildings can make things worse by drawing large amounts of moisture from the ground - species like oak, poplar, and willow are particularly thirsty.
Enter your postcode above for an area-level indication based on British Geological Survey shrink-swell data. The result shows whether the ground beneath your postcode falls into the Lower, Medium, or Higher band for clay-related movement potential. For a property-specific assessment - especially before buying - a structural survey or the BGS Property Subsidence Assessment service provides more detail.
Three levels of check are available. Free postcode-level: LocalRisk returns an area band in 5 seconds. Free address-level: the BGS GeoIndex Onshore viewer shows the underlying geological classification. Paid: the BGS Property Subsidence Assessment service for transactions or insurance underwriting. LocalRisk council pages also show the share of Higher-band postcodes by local authority.
Shrink-swell subsidence is the most common form of ground movement affecting UK homes. Clay soils - notably London Clay, Oxford Clay and Lias Clay - expand when wet and contract when dry, cracking walls, distorting frames, and in severe cases requiring underpinning. An estimated 4.5 million UK homes sit in shrink-swell areas, concentrated in southern and eastern England.
A documented subsidence history can affect saleability and price; the discount depends on severity, repair quality and wider property attributes. Sales of properties with a subsidence history take longer to complete because of the extra documentation buyers and their advisers review. Being in a high-risk area without any actual subsidence does not carry the same effect, but is still worth knowing before purchase.
No. Flood Re helps make flood insurance affordable for eligible high-risk homes, but there is no equivalent for subsidence. Cover is handled through the standard insurance market. Most buildings policies include subsidence as standard, but the excess is typically higher - often around £1,000 - and a documented claims history or higher-risk postcode can affect what insurers offer.
Subsidence risk is highest where clay soils are most common: south-east England, London, the Thames Valley, and parts of the Midlands. The BGS identifies these areas as having moderate to high shrink-swell potential. As summers grow hotter and drier, the at-risk zone is projected to spread further north and intensify in the south.
Manage trees and large shrubs - especially water-hungry oak, poplar and willow - near foundations. Maintain gutters, pipes and drainage to prevent uneven water pooling around the building. Watch for early warning signs: new or widening diagonal cracks around windows and doors, sticking doors, or gaps where walls meet ceilings. An arborist can advise on planting distances.