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Check coal mining risk, radon potential, shrink-swell clay and bedrock geology for any UK site — 26 ground risk layers essential for geotechnical desktop studies.
Updated: monthly for Coal Authority layers · Last checked by Maplify: July 2026
This layer combines 26 geology and ground risk datasets: Coal Authority Development High Risk Areas and surface coal resources, historic landfill sites, and BGS GeoSure hazard ratings covering radon potential, shrink-swell clay, landslide susceptibility, compressible and collapsible ground, running sand and soluble rock dissolution, alongside 1:50,000 scale bedrock and superficial geology.
Together these give a screening-level picture of the ground conditions and past land use that shape foundation design and site investigation scope.
Ground risk directly affects foundation design, construction cost and, for coal mining areas, whether a Coal Mining Risk Assessment is required before planning permission can be granted. Developers, engineers and surveyors check this layer at feasibility stage to scope what a site investigation should specifically test for, rather than commissioning an unfocused geotechnical survey.
Because these hazards are often invisible at surface level, early desktop screening avoids discovering a costly ground constraint only after a site has been acquired or a scheme has progressed to detailed design.
Coal Mining High Risk Area
Recorded mining features that could affect surface stability — a Coal Mining Risk Assessment is typically required.
Radon Potential
BGS-modelled probability that new buildings would need radon protection under Building Regulations.
Shrink-Swell Clay
GeoSure hazard rating for clay soils that expand and contract, affecting foundation depth.
Sites within a Coal Authority Development High Risk Area typically require a Coal Mining Risk Assessment (CMRA) submitted alongside the planning application, while high radon potential triggers Building Regulations protection measures for new dwellings. Shrink-swell, landslide and dissolution hazard ratings inform structural engineering and foundation design, sometimes requiring deeper or more specialist foundations.
None of these hazards typically prevent development outright, but they add cost, technical complexity and, for coal mining, a mandatory pre-application assessment step.
Confirm the exact hazard classifications with BGS and the Coal Authority for the specific site.
Commission a Coal Mining Risk Assessment if the site falls within a Development High Risk Area.
Factor radon protection measures into the design if the site falls within an elevated radon zone.
Scope a geotechnical site investigation informed by the specific hazards flagged on this layer.
Check the Coal Mining Risk, Geology Maps and Contaminated Land layers individually for more detail.
This is general guidance, not professional or legal advice — confirm specifics with the relevant authority or a qualified professional.
Property Developers
Scope ground investigation and Coal Mining Risk Assessment requirements before acquisition.
Structural Engineers
Inform foundation design decisions from shrink-swell and landslide ratings.
Surveyors
Factor ground risk into valuation and building survey reports.
Planning Consultants
Advise on likely conditions relating to ground stability and radon.
Ground risk checks are often run alongside these related searches.
What ground risk data does the map cover?
Coal mining high risk areas, radon potential, shrink-swell clay, landslide susceptibility, compressible ground, dissolution hazards, historic landfill and BGS bedrock and superficial geology — 26 layers in total.
Do I need a coal mining search for my property?
If the property falls within a Coal Authority Development High Risk Area, a CON29M coal mining report is typically required for conveyancing and may be mandated by mortgage lenders.
What does high radon potential mean for a new build?
Building Regulations Approved Document C requires radon protection measures — such as a radon barrier — for new buildings in areas the BGS identifies as having elevated radon probability.
How does shrink-swell clay affect building foundations?
Clay that expands when wet and shrinks when dry can cause seasonal ground movement. BGS GeoSure hazard ratings guide foundation depth, with higher-risk areas often needing 1–2m deep foundations.
Is this ground risk data a substitute for a site investigation?
No. It is a desktop screening tool to scope what a site investigation should look for — a full geotechnical investigation with boreholes or trial pits is still needed to confirm actual ground conditions.
Search any UK site to see all 26 geology and ground risk layers in one view.
| Provider | British Geological Survey / Coal Authority |
| Geometry type | Polygon |
| Coverage | England |
| Update schedule | Monthly for Coal Authority layers; periodic for BGS datasets |
| Reference date | July 2026 |
| Licence | Open Government Licence v3.0 |
