It is a real scourge which continues to grow in France and leaves thousands of French people distraught when they see their house – often the project of a lifetime – cracked with deep cracks which threaten the structure of the building, the facades , load-bearing walls, floors or frames. The phenomenon of shrinkage-swelling of clays (RGA) which is at the origin – soil movements linked to their drying – is not new. It is even perfectly known to scientists and it is the subject of close monitoring, particularly by the Bureau of Geological and Mining Research (BRGM) which maps it.
But for several years now, the number of claims has been increasing exponentially, as droughts multiply and intensify under the influence of global warming, making this phenomenon a real “social bomb” in terms of housing. .
48% of the French territory – 49% in Occitanie – are in a medium or high exposure zone and the outlook is not encouraging as shown by the recent study conducted by the Conséquences association or the figures from France Assureurs. 16.2 million houses could be exposed to medium or severe hazards by 2050 if climate warming continues and adapting all of these houses could cost up to 7 billion euros per year. While the financial impact of the RGA on the natural disaster regime (Cat Nat) exploded in 2022 to amount to more than 3 billion euros, it is the entire structure of compensation for disaster victims which is in crisis. Danger.
The shrinkage-swelling of clays places us at the back of the wall and requires us to act on at least three axes. First, find mechanisms for fair compensation for victims, many of whom are undergoing a grueling obstacle course. Disputes between victims, mayors and insurers are unfortunately common, and generate incomprehension and anger. Deputies and senators were recently divided over Sandrine Rousseau’s bill aimed at expanding compensation and the municipalities eligible for the natural disaster regime. However, we will have to find a way through.
The second axis is of course the prevention of this phenomenon and the adaptation of exposed houses. The work is possible but often heavy, complex and expensive; and construction standards must be able to improve. Here too, we must find a way so that the French people affected are helped if necessary and well warned.
Finally, the last axis, undoubtedly the most difficult, involves reviewing our land use planning policies by linking them to the consequences of global warming, current and modeled for years to come. We will need to have the political courage to declare certain areas unconstructible, or even destroy certain homes and rehouse their occupants in new, safer houses, new neighborhoods. A major challenge that we have no choice but to take on.