One risk indicator, several public data sources
The foundation risk indicator shown in PlotSense's Foundation Report is not a single loose estimate — it is the result of combining several independent, public data sources into one indicator per address. None of these sources is sufficient on its own to make a reliable statement about foundation risk — only the combination produces a usable picture.
Which data sources does PlotSense use?
- Construction year and building data (BAG): the Dutch national address and buildings register provides the official construction year and some structural characteristics of a property. Construction year is a strong indicator because it correlates with the likelihood of a wooden pile foundation (see the article on when a physical survey is needed).
- Soil and peat data (BRO GeoTOP): the national 3D soil model provides peat thickness, depth and soil type per parcel at a resolution of roughly 100 metres (see the article on peat, groundwater and subsidence).
- Groundwater and subsidence data (Deltares): average highest groundwater level (GHG) and subsidence figures per year, sourced from the Dutch research institute for water and soil issues.
- The public FCAB foundation map: an independently published, national reference at building-type and area level, which PlotSense uses as a cross-check alongside its own address-specific assessment (see the article on why FCAB and PlotSense can differ).
Why combine multiple sources?
Each source has its own limitations. The BAG doesn't record foundation type; BRO GeoTOP is spatially modelled and therefore not an exact boring on your parcel; Deltares data changes over time; and FCAB works at area level rather than per address. By combining these sources and cross-checking them against each other, the PlotSense approach corrects for the weak spots of any single source. An address where construction year, soil context and groundwater trend independently all point to elevated risk gives a stronger signal than when only one source paints that picture.
A risk indicator, not a guarantee
The result of this combination is one risk indicator per address, presented alongside a comparison with the public FCAB map. An elevated indicator is not a guarantee of damage — it's a signal that the likelihood of foundation problems at this address is above average, and that further investigation may be worthwhile (see the article on when a physical foundation survey is needed).
A worked example: a home built in 1932
To show how the data sources come together: a home built in 1932, in an unfavorable location (low, wet subsoil, thin peat layer, declining groundwater level), combines an old construction year with a risky soil context. Construction year is a heavy factor here: homes built before roughly 1970, and especially before the Second World War, are in large parts of the Netherlands founded on wooden piles, and the likelihood that the foundation was never replaced or reinforced increases the older the construction year. Combined with an unfavorable soil context (see the next article on peat and groundwater), such a combination of signals results in a clearly elevated risk indicator for that address.
A reliability note belongs with it
Not every input is equally solid. Foundation type, for instance, is not recorded in any national dataset and is therefore weighed as a less certain input. To avoid the report implying more certainty than the source data supports, the Foundation Report also includes a note on how reliable the underlying data is for your specific address. When data reliability is low, we recommend weighing the details yourself rather than trusting a single indicator blindly. This matters most for foundation type: that data point is not recorded in any national dataset (see the article on peat, groundwater and subsidence for the details).
What this means for you as a buyer or owner
When reading your Foundation Report (€35), it's worth looking not just at the risk indicator but at the underlying data: construction year, soil context, the comparison with the FCAB map, and the reliability note. Check your own address at plotsense.app/zoek or read more about the Foundation Report (€35).