Data sources and method
Where each part of the report comes from, at what scale, and how the results are worked out.
Every report is built live from public datasets when you search. Nothing is estimated from neighbouring postcodes or invented. Where a source does not respond, the report says so rather than guessing.
Sources
| Data | Provider and service | Coverage and scale | Used for |
|---|---|---|---|
| Postcode location | postcodes.io (ONS Postcode Directory, Ordnance Survey Code-Point Open) | UK, postcode centre | Starting pin, area names, region |
| Bedrock and superficial geology | BGS Geology 625k, BGS OGC API Features | Great Britain, 1:625,000 | Soluble rock, clay bedrock, soft deposits, coal-bearing rocks |
| Soil parent material | BGS Soil Parent Material Model, UK Soil Observatory WMS | Great Britain, 1 km derived from 1:50,000 geology | Soil texture, clay content, depth, carbonate |
| Peat | BGS Peat Coverage (derived from 1:50,000 geology), UK Soil Observatory WMS | Great Britain | Compressible ground |
| Trees | Forest Research Trees Outside Woodland map (ArcGIS feature services) | England only; lone trees, groups and small woodland, not woodland over 0.5 ha | Canopy outlines, heights, distances |
| Landslides | BGS National Landslide Database index, OGC API | Great Britain, within 2 km | Recorded ground movement |
| Boreholes | BGS onshore borehole index, OGC API | Great Britain, within 250 m | Links to logs showing actual ground conditions |
| Mine plans | BGS mine plans index, OGC API | Great Britain, within 1 km (borehole site maps excluded) | Historic mining nearby |
| Tree water demand | NHBC Standards Chapter 4.2, Table 3 | – | Zone of influence (1.25 / 0.75 / 0.5 × mature height) |
| Base map | OpenStreetMap | – | Map display |
How each indicator is worked out
Sinkholes and dissolution
Higher where the mapped bedrock includes gypsum, anhydrite or salt, or is in the Permian Zechstein Group. Moderate for chalk, limestone or dolomite, and for the Mercia Mudstone Group, which can contain gypsum and salt beds. Lower where none of these is mapped.
Shrink–swell clay
Points for a heavy or clay-textured soil (2), some clay in the soil (1), clay or mudstone bedrock with no superficial deposits mapped over it (1), and clay-bearing superficial deposits such as till or brickearth (1, unless the soil model shows sandy ground). Three or more is Higher, one or two is Moderate, none is Lower. Peat soils show Moderate here and are assessed under soft ground.
Trees near the building
Each mapped canopy within 50 m of the pin is given a zone of influence of 1.25 × its maximum canopy height (high water demand, because species is unknown). Trees you add with a known species use the NHBC category and the larger of the height you give and the species’ mature height. If any tree’s zone reaches the pin, the indicator follows the shrink–swell result: Higher on Higher clay, Moderate on Moderate clay, Lower on non-shrinkable ground.
Soft or compressible ground
Higher for peat. Moderate for alluvium, estuarine, tidal, lake or marine deposits, or for loose sand or gravel over soluble rock.
Recorded movement and mining
Higher for a recorded landslide within 250 m, or mine plans within 1 km on coal-bearing rocks. Moderate for a landslide within 1 km, mine plans within 1 km, or coal-bearing rocks. Otherwise Lower.
Limitations
- Scale. The 1:625,000 geology can place a boundary hundreds of metres from its true position and omits thin local deposits.
- Location. Results are for the pin. A postcode centre can be some distance from a particular house until you move the pin.
- Trees. England only, no species, current height only, and woodland over 0.5 ha is excluded. Trees planted or felled since mapping will not show.
- Not included yet. BGS GeoSure hazard ratings, the BGS Property Subsidence Assessment, GeoClimate projections, Mining Remediation Authority (Coal Authority) records, flood and groundwater data, and drainage records. These are licensed or not yet connected.
- No address search. Selecting an individual address needs a licensed address service. Use the pin instead.
Licences and attribution
- Contains British Geological Survey materials © UKRI 2026, used under the Open Government Licence.
- National Trees Outside Woodland Map © Forestry Commission copyright and/or database right 2025, published by Forest Research under the Open Government Licence.
- Postcode data: Contains OS data © Crown copyright and database right 2026; Contains Royal Mail data © Royal Mail copyright and database right 2026; Contains National Statistics data © Crown copyright and database right 2026. Served by postcodes.io.
- Map data © OpenStreetMap contributors.
- Tree water demand from NHBC Standards Chapter 4.2. NHBC is not associated with this site.
Method and sources checked 1 November 2026.
Check a postcode
See the geology, soil, nearby trees and BGS records for any UK postcode, explained.