Quarries and subsoil of Paris’s 20th arrondissement
Moderate risk Paris 75020
The 20th arrondissement (Belleville, Ménilmontant, Père-Lachaise) presents a gypsum-related risk on the Belleville and Ménilmontant hills, which were mined for plaster. Gypsum, which is soluble in water, presents a risk of dissolution and sinkholes (fontis), aggravated by pipe leaks and the lack of suitable drainage. No major recent event has been documented there, but the risk remains present on the hills of eastern Paris.
What public data say about the 20th
| Underground network | Gypsum quarries (east) |
|---|---|
| Mined rock | Antediluvian gypsum |
| Undermined area | Part of the 65 ha of Paris gypsum. |
| Galleries | Gypsum network. |
| Selected risk level | Moderate |
| Confidence in the classification | high |
| Nature of the ground | Belleville/Ménilmontant hills: limestone + gypsum |
| Foundation issue | A geotechnical study is recommended, with particular attention to gypsum dissolution and the condition of buried water networks before any purchase of land or construction project. |
Sensitive areas of the 20th
- Buttes de Belleville and Ménilmontant, Père-Lachaise
- Gypsum mined for plaster on the eastern hills
Ground, fill and clay shrink-swell
The 20th arrondissement has Brie plateau limestone at the surface and Antediluvian gypsum at depth on the Belleville and Ménilmontant hills (see quarry section).
A geotechnical study is recommended, with particular attention to gypsum dissolution and the condition of buried water networks before any purchase of land or construction project.
Unlike almost all French municipalities, inner Paris has no official mapping of the clay shrink-swell hazard (RGA). The BRGM explains this explicitly: the Paris subsoil is largely made up of reworked and artificial materials (backfill, infilled former quarries), which does not correspond to the standard methodology for this mapping — centred on detached houses, which are in the minority in Paris. This does not mean that there is no risk of differential settlement, but that no official area-by-area study exists for the capital: a ground investigation remains the only reliable way to assess a specific plot before purchase or construction.
Your steps to take in the 20th before a purchase or works
Gypsum risk present: consultation with the IGC (Paris quarry inspectorate) (€10, < 8 days) and a geotechnical study are recommended before purchase or works, especially on the Belleville and Ménilmontant hills.
- IGC (Paris quarry inspectorate) information sheet — the authoritative source on the condition of the parcel’s subsoil: €10, issued within 8 days, via the City of Paris online service.
- Statutory risk statement (ERP) — mandatory for sale and letting, generated from Errial; note, it does not return cavity data in Paris.
- geotechnical survey — G1 mission before purchasing a building plot, G2 AVP before a construction or underpinning project.
- Referral to the IGC (Paris quarry inspectorate) for planning — prefectoral orders require it to be consulted for any planning permission in a quarry-risk area.
Frequently asked questions
Are there underground quarries beneath Paris’s 20th arrondissement?
Yes. The 20th arrondissement is recorded in public data from the IGC (Paris quarry inspectorate) as an area affected by the « Gypsum quarries (east) » network, in Antediluvian gypsum. The risk level selected is « Moderate », with high confidence in the sector classification. The Belleville and Ménilmontant hills were mined for gypsum. Risk of dissolution and sinkholes (fontis), aggravated by water circulation (leaks from pipes). Belleville / Père-Lachaise / Ménilmontant sector.
How can I tell whether my specific address in the 20th is in an undermined area?
Quarry zoning must be read at plot level rather than arrondissement level. There are two options: the official information sheet from the IGC (Paris quarry inspectorate), at €10 and issued within 8 days, which is the legally binding source; and Sous-sol Paris’s instant pre-assessment, at €15, which matches your address against public data and immediately provides you with a readable report, including the steps to take. This pre-assessment is for information only and does not replace the IGC information sheet, the statutory risk statement (ERP), or a geotechnical study.
Why do the 20th’s cavity data not appear on Géorisques?
Because for départements 75, 78, 91, 92, 93, 94 and 95, cavity data are not published on the Géorisques portal: they can be consulted with the IGC (Paris quarry inspectorate) for Paris and the inner suburbs, or with the relevant interdepartmental service. This is why a standard statutory risk statement (ERP) remains silent on Paris quarries and gypsum.
Is quarry risk in the 20th covered by insurance?
Disorders linked to former quarries do not fall under the « natural disaster » scheme. In the event of collapse, infill works, estimated at 40 000 to 200 000 €, remain the responsibility of the owners. This is what makes checking before purchase essential.
Other arrondissements
- Subsoil of the 19th arrondissement
- Subsoil of the 18th arrondissement
- Subsurface of the 17th arrondissement
- Subsoil of the 16th arrondissement
- Subsoil of the 10th arrondissement
- See the 20 arrondissements
Sources
- City of Paris — Everything you need to know about the subsurfaces
- DRIEAT Île-de-France — Risks related to underground cavities
- BRGM — Why is there no map of the clay shrink-swell hazard for Paris?
- Géorisques — Clay shrink-swell, 2026 version (data)
- Géorisques — Underground cavities (data)
- City of Paris — the IGC (Paris quarry inspectorate) location
- City of Paris — Known areas of former quarries (IGC)
Page updated on 11 September 2026.