The government will publish a map to alert 12.1 million owners. 6 out of 10 houses could lose their real estate value and be prohibited from renting. 9 regions are particularly concerned.
The threat is as discreet as it is devastating. Clay shrinkage-swelling (RGA) is a climatic phenomenon which affects millions of homes across France, causing cracks so significant that some homes become uninhabitable. Impacted owners can no longer sell or rent them.
The fault is global warming which causes waves of drought in France every year. When heatwaves occur, clay soils contract, causing building foundations to sink. Then, when the fall showers return, the ground expands and the foundations rise. This is where spectacular cracks appear on the walls.
On January 9, the government published a decree updating the mapping of areas exposed to RGA. This new map, developed by the Bureau of Geological and Mining Research (BRGM), will be available for consultation from July 1, 2026 on the portal georisks.gouv.fr. The “medium or high” RGA risk zones now cover 55% of the metropolitan territory, compared to only 48% in 2020. Concretely, 12.1 million individual homes are today threatened by the RGA, which represents 61.5% of houses in mainland France.
The Consequences association, which is dedicated to studying the effects of global warming, analyzed claims relating to RGA and recognized as natural disasters by insurance companies. She notes an explosion of cases in certain departments. By comparing claims declared between 1989 and 2005, then those declared between 2006 and 2022, certain departments show a number of claims increasing by 1,000%!
This is the case in the department of Haute-Marne and in the department of Gard, where the number of claims linked to RGA increased by 1,132% and 1,032% respectively. The other departments where the evolution of losses caused by the RGA is obvious are the Loire (+738%), Haute-Saône (+638%) and Bas-Rhin (+568%).
More generally, the Central Reinsurance Fund (CCR) specifies that “more than 20 million French people currently reside in areas classified as medium or high risk”. Certain regions are particularly at risk. In the Centre-Val de Loire, 67% of individual houses are threatened. Occitanie comes in second place with 49% of houses concerned, followed by Nouvelle-Aquitaine where 46.8% of houses are subject to the RGA. Burgundy-Franche-Comté has 44% of housing at risk, while the Provence-Alpes-Côte d’Azur region has 39%. Hauts-de-France shows a rate of 33% of houses concerned, Pays de la Loire 32%, Île-de-France 28%, and Grand Est 26.5%.
Projections for the future are even more worrying. The Consequences association anticipates a major worsening of the phenomenon. According to its estimates, “the number of homes threatened by RGA will reach 16.2 million by 2050”. By this deadline, 92.8% of individual homes in mainland France would be exposed to this risk. A coming earthquake for the real estate stock, for the insurance market and especially for the owners of the impacted houses.
