” Unprecedented. » In the summer of 2022, drought affected a large part of French territory, particularly farms. However, dry weather also aggravates the phenomenon of clay shrinkage-swelling (RGA), which potentially concerns 10.4 million individual houses in France, according to a study by the General Commission for Sustainable Development.
These alternating movements of clay soils thus depend, among other things, on climatic conditions: in rainy periods, waterlogged, the soil “swells”, and conversely, in dry weather, it “shrinks”. But when this retraction period drags on, the ground cracks the frame.
Requests rejected
” A disaster “remembers Alain Boulanger, the mayor of Fléville-devant-Nancy (Meurthe-et-Moselle), located in the Nancy conurbation, a « cuvette » on clay soil, which has seen a proliferation of disputes as the rain becomes scarce in summer. To get redress, the city councilors are responsible for identifying cases of RGA in their municipality and presenting them to an interministerial commission. This is part of the recognition system, called “Cat Nat”, provided for by the insurance code.
This commission, headed by the Ministry of the Interior, is responsible for recognizing the state of natural disaster for one year. Such recognition theoretically allows owners to be compensated by insurance companies for damage caused by RGA.
But the request of Alain Boulanger and elected officials from Lorraine was rejected by the interministerial commission, like about half of the 5,000 to 6,000 requests under the RGA made each year. This system is widely criticized by victims’ associations, lawyers and elected officials. “We have a weather information system that is not precise enough to be able to decide that a municipality has suffered an RGA phenomenon”explains Christine Lavarde, LR senator for Hauts-de-Seine, author of an information report on the subject in 2022.
“Better compensation for property damage” generated by the phenomenon, this is the subject of the bill debated this Thursday, April 6 in the National Assembly. Filed within the framework of the parliamentary niche of the environmental group, the text proposes a modification of the insurance code, according to several principles.
Expand criteria
On the one hand, they wish to broaden the criteria of the regime: when the year in question is one of the ten driest years for fifty years, the state of natural disaster would be automatically recognized.
The second article aims to establish a presumption of the origin of the damage. “As soon as there is recognition in the municipality, it is assumed that the damage comes from the drought. And insurance would be obliged to prove the opposite”explains François Manneville, president of the Lorraine cata drought association, which supports the environmental proposal.
The issue of financial sustainability
“This gives more power to citizens in the face of insurance” , salutes Me Antoine Loctin, of the firm CL Avocats, who supports elected officials in the region in their litigation. A welcome rebalancing, because the Cat Nat diet is “an insurance mechanism for which everyone contributes obligatorily, without knowing it, as soon as one has a home insurance contract or a car insurance contract”summarizes Christine Lavarde.
But such an expansion raises the question of the financial sustainability of the system, while droughts are likely to increase in the coming years. Eventually, such a development could cost 850 million euros per year, according to estimates by the Central Reinsurance Fund (CRR). While waiting for better compensation, the senator points out the lack of prevention and investment in research and development to respond to this risk.
Find solutions
For the time being, researchers from the Center for Studies and Expertise on Risks, the Environment, Mobility and Planning (Cerema) are experimenting with the house system comforted by humidification plus (Mach+). “We will collect rainwater during the wet period and store itexplains Lamine Ighil Ameur, researcher in soil mechanics at Cerema. During the drought period, the soil will be re-moistened gradually, below the formation footing. »
For their part, the new owners of Lorraine could look towards Luxembourg and Germany, where, according to geotechnical engineer Dominic Torlini, constructions on rafts, a “large concrete slab on which the house rests”are legion.
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48% of the territory potentially concerned
In France, 48% of the territory has clay soil and can therefore be affected by the phenomenon of shrinkage-swelling of clays (RGA). To find out if your property is affected, go to the government website Errial Georisks.
La Loi Elan, voted on November 23, 2018, makes it compulsory to carry out soil studies in clay risk areas for the construction of a house. Preventive and constructive measures can be taken to build safely.
In 2022, the total cost of claims linked to the RGA phenomenon was valued at more than 2.5 billion euros, says a Senate information report published in February 2023. The average cost of compensation is estimated at €16,700, i.e. the highest of the guarantees damage.