"It's scary": When droughts cause houses to crack

Their single-storey dwelling, built on clay soil, is subject to the movements of the ground, which swells with humidity and settles in times of drought.

In 2003, the year of a memorable heat wave, the first cracks had appeared. Their town, Coulaines (Sarthe), near Le Mans, had been classified as a state of natural disaster and the insurance had paid to redo the damaged walls.

But in the summer of 2020, the most serious "staircase" cracks appeared again on one wall of the house. Then on a second in 2022.

"When we saw the wall like that... it's scary," says Jean-Luc Chisson, a 62-year-old former delivery driver.

President of the Urgence Maisons fissurées Sarthe association, which claims 400 members, Mohamed Benyahia sees his house, in the neighboring town of Neuville-sur-Sarthe, crossed since 2018 by an impressive crack, which curative works have not resorbed.

"Since September 2018, I no longer live the same way. More personal activities, more leisure...", confides this 62-year-old computer engineer. "Even the desire to have a barbecue, I no longer have it".

Who pays ?

Like them, millions of French people are vulnerable to the so-called risk of "clay shrinkage-swelling".

Called to worsen with global warming, which accentuates the frequency and intensity of droughts, it threatens especially individual houses, with shallow foundations. More than 10 million, or one in two, are built on soil classified as medium or high risk.

A situation that poses a major economic problem: who pays for the costly repair and prevention work?

In France, the risk is covered by the natural disaster insurance scheme. But many victims fail to obtain compensation.

In Coulaines, around forty houses cracked following the scorching summer of 2022. But in the absence of a ministerial decree of natural disaster including their municipality, no one could be compensated.

"We can only watch the house crumble!", creaks Sylvie Chisson. In 2020, she was not entitled to anything either, for the same reasons.

"What we do not understand are the differences in treatment from one municipality to another", laments the mayor (PS) of Coulaines, Christophe Rouillon.

"What makes a municipality 10 kilometers away is selected while another is not? With land that is the same, temperatures that are the same..."

Tripled costs

It is this defect that intends to tackle a bill brought by the ecologist Sandrine Rousseau, adopted at first reading in the National Assembly.

"It's a law that takes protection against global warming head on. Because there, one house in two is threatened, which means that if you let it happen, neither the insurers nor the State will be able to to manage. And so things have to be changed so that the state can anticipate, "explains the deputy to AFP.

The text provides for facilitating the recognition of the state of natural disaster in the affected municipalities. And where it has been recognized, it makes it harder for insurers to deny claims.

"It's really a change in the balance of power of the policyholders in relation to the insurers. Often, the insurers try to show that it is not the shrinkage-swelling of the clays the main cause of the disorders, which leaves the owners in their great difficulty," she said.

This last measure is met with opposition from insurers, who estimate that it would cost them an additional 1 billion euros each year.

“Such a decision would have a very, very significant financial impact on the financial balance of the scheme, which has already been in deficit for several years”, advances the president of France Assureurs, Florence Lustman.

According to this federation, over the period 2020-2050 and with constant regulation, the cost of claims related to the shrinkage-swelling of clay should triple compared to the previous thirty years, and increase from 13,8 to 43 billion euros.