Clay soil on the French Riviera: why your commune matters
Large parts of the Alpes-Maritimes, Var and Bouches-du-Rhône are built on clay-rich ground that swells in wet periods and shrinks during droughts — the phenomenon known in France as retrait-gonflement des argiles (RGA). Each dry summer, this movement cracks walls, jams doors and windows and, in the worst cases, affects foundations. The BRGM, the French geological survey, publishes a clay shrink-swell exposure rating for every commune, and a geotechnical study has been mandatory since 1 October 2020 before building on plots zoned medium or high exposure. The table below gives the official rating for the 32 communes where we most often carry out crack and subsidence surveys, with a dedicated page of official data for each one.
The 32 communes and their BRGM clay exposure level
| Commune | Dept. | BRGM clay shrink-swell exposure |
|---|---|---|
| Antibes | 06 | High |
| Beausoleil | 06 | High |
| Biot | 06 | High |
| Brignoles | 83 | High |
| Cagnes-sur-Mer | 06 | High |
| Cannes | 06 | High |
| Carros | 06 | High |
| Draguignan | 83 | High |
| Fréjus | 83 | High |
| Grasse | 06 | High |
| Hyères | 83 | High |
| La Crau | 83 | High |
| La Seyne-sur-Mer | 83 | High |
| La Valette-du-Var | 83 | High |
| Le Cannet | 06 | High |
| Le Muy | 83 | High |
| Le Pradet | 83 | High |
| Mandelieu-la-Napoule | 06 | High |
| Menton | 06 | High |
| Mougins | 06 | High |
| Nice | 06 | High |
| Ollioules | 83 | High |
| Saint-Raphaël | 83 | Medium |
| Sainte-Maxime | 83 | Medium |
| Sanary-sur-Mer | 83 | High |
| Six-Fours-les-Plages | 83 | High |
| Toulon | 83 | High |
| Valbonne | 06 | Medium |
| Vallauris | 06 | High |
| Vence | 06 | High |
| Vidauban | 83 | Medium |
| Villeneuve-Loubet | 06 | High |
Source: BRGM clay shrink-swell zoning (GéoRisques platform), commune-level rating; sector-by-sector maps can be more detailed. Working in the Sophia Antipolis area? See our Sophia Antipolis clay soil and subsidence data page.
Cracks appearing? What an independent survey gives you
A commune rating is only the starting point: an independent crack and subsidence survey establishes the cause of the damage, dates it against the rainfall record and quantifies repairs — the technical evidence your insurer or CATNAT drought claim will rely on. Cassini Expertise covers departments 06, 83 and 13 from Antibes; ask for a free quote — reply within 24 hours, reports written in English.
📅 Last updated 24/10/2026 - Cassini Expertise, independent building expert – departments 06, 83 and 13.