Ground Risk Checker
Check coal mining history and clay subsidence risk for any UK postcode. Based on Coal Authority mining risk maps and BGS GeoSure data.
Understanding ground risk when buying a property
Ground risk covers two main concerns for UK property buyers: coal mining subsidence in former coalfield areas, and shrink-swell clay subsidence caused by expansive clay soils. Both can lead to structural damage if not identified during the buying process.
Coal mining risk is highest in areas overlying historic coalfields — Yorkshire, South Wales, County Durham, the Midlands, and parts of Scotland. Shallow workings, mine entries, and the collapse of old tunnels can cause sudden or progressive ground movement. The Coal Authority maintains records and offers official mining reports.
Clay subsidence is most prevalent in London and the South East, which sit on London Clay — a highly expansive soil that swells when wet and shrinks when dry. This seasonal movement can cause significant structural damage, particularly in older properties or those near large trees.
Frequently asked questions
- What is a Coal Authority search?
- A Coal Authority mining search is a report that confirms whether a property is in a coalfield area and whether there are any recorded mine entries, workings, or active subsidence claims nearby. It costs around £30–£40 and is usually included in a standard conveyancing search bundle. It covers England, Wales, and Scotland.
- How does clay subsidence affect buildings?
- Clay soils expand when wet and contract when dry, causing seasonal ground movement. This is most pronounced in dry summers and can cause cracking in walls, sticking doors, and uneven floors. Properties on clay soil near large trees are particularly at risk as tree roots extract moisture. Buildings on clay with shallow foundations (common pre-1950) are most vulnerable.
- Will ground risk affect my mortgage or insurance?
- Mining risk rarely affects mortgage availability directly but lenders may require a Coal Authority search. Clay subsidence can affect insurance — particularly for older properties near trees. If a property has existing subsidence damage, insurers may exclude it or apply higher excesses. Always disclose known subsidence history when applying for insurance.
- What survey should I get in a high-risk area?
- A Level 3 Building Survey (formerly known as a Full Structural Survey) is recommended for properties in coal mining or high clay subsidence areas. It includes a detailed inspection of the structure, foundations, and any evidence of movement. This costs more than a Homebuyer Report (Level 2) but provides far more detail on ground-related risks.
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