How do you know whether there is a mine shaft or karst under a plot?

In Wallonia the SPW keeps maps of what makes the subsoil uncertain: mine shafts, underground quarries, old iron workings, karst and slopes where rocks can fall. If a plot lies in such a zone, the municipality can refuse a permit or impose conditions (CoDT art. D.IV.57, 3°), and the planning information mentions it (art. D.IV.97, 9°). A free sheet from the subsoil service states what is known for a single property.

What can lie under the ground

Mine shafts (puits de mine): the entrances to old coal mines. The map also shows possible shafts from before 1791, whose location is not always certain.
Underground quarries: old workings of, among other things, marl and slate.
Iron workings (minières de fer): old extraction of iron ore.
Karst: cavities that water wears into limestone, which can make the ground subside.
Rockfall and landslides: steep slopes where stones or soil can slide.

Other things often matter on the same plot too, such as Walloon heritage and the BDES and its extract. You can see how a report brings them together in the sample report.

The subsoil information sheet

The SPW’s Direction des risques industriels, géologiques et miniers (DRIGM) provides on request a subsoil information sheet (fiche d’information sur le sous-sol) for one property: free, within ninety days and valid for six months. You request it through Mon Espace, the Region’s online counter. On WalOnMap you can see the zones de consultation: where the service is consulted beforehand. These zones are indicative and incomplete.

For a building project

In such a zone the municipality can ask for the DRIGM’s opinion on a permit. That can lead to a ground study, adapted foundations or a refusal. Budget for that study before you make an offer on building land in a zone de consultation.

Mining damage

Shafts and galleries legally belong to the mine, not to the land above (mining decree of 7 July 1988, art. 14 and 19). Whoever held the concession must repair damage caused by the mining works, even after the concession was withdrawn (art. 42 and 46); a dispute first goes to conciliation and then to the justice of the peace (art. 43 and 44). For a concession that disappeared long ago there is sometimes nobody left to claim from: have the notary check this.

What the Perceelscan shows

Section 12 of the report shows what the subsoil map indicates on or near the plot: a mine shaft, a possible old shaft, an underground quarry, an iron working, karst or rockfall. It does not replace the DRIGM information sheet.

Is a plot near a mine shaft unbuildable?

Not necessarily. The municipality can impose conditions, such as a ground study or a distance from the shaft, or refuse the permit. Request the subsoil information sheet before you buy.

What does the subsoil information sheet cost?

Nothing. The SPW provides it free of charge, within ninety days, and it stays valid for six months.

Sources

Check it for your address

Updated on 26 October 2026