2023-09-14 18:54:52
Acronym for shrinkage-swelling of clays, RGA is a geological phenomenon that is as simple as it is damaging. The mechanism at work? Buildings built on clay soils suffer from their extreme sensitivity to water. When it rains, they swell. Conversely, they shrink when drought hits.
A back and forth movement that pulls the soil apart and pulls the foundations of the houses on both sides. The result is a building that becomes fragile, cracks appear along the walls, land that loses value and homes that are sometimes uninhabitable because they are dangerous.
To deal with this, French insurers announced on Tuesday September 12 a “drought initiative”. “We want to improve knowledge of the risk of drought in order to offer the French prevention services and repair solutions that meet the challenge”explains Florence Lustman, president of the French Insurance Federation, at the base of the project alongside the Central Reinsurance Fund and the Mission Natural Risks association.
A growing phenomenon
Because the expenses due to the RGA are becoming more and more critical. While the cost of claims represented 400 million euros per year between 1989 and 2015, it increased to one billion over the period 2016-2020, then to 3 billion euros for the year 2022 alone.
The phenomenon has increased considerably in recent years, due to global warming, repeated droughts and floods. And if it mainly concerned the Var, the Garonne basin or even the Centre-Val de Loire, it now extends to the Grand Est, Burgundy-France-Comté and Auvergne-Rhône-Alpes regions.
In September 2023, 11.1 million individual houses were affected, or almost half of the stock. Nearly 3.3 million of them would even be “heavily impacted”.
An experimental phase
To adapt, the drought initiative is giving itself five years to test the solutions currently imagined. Installation of piles under the foundations, to stabilize and anchor the house in the firmer rocks located under the clay layers; injection of resin into clay soils to compact it; installation of a geomembrane on the ground, to prevent humidity from evaporating during periods of drought. The solutions are diverse.
Some of these methods have already proven themselves, such as the system imagined by Lamine Ighil Ameur. “The principle is simple: in winter, rain is collected in tanks placed around the house, and in summer, sensors detect any phase of drought and then irrigate the clay soils with this water”, explains this soil mechanics researcher at the Center for Studies and Expertise on Risks, Mobility and Development (Cerema). The cracks are thus stabilized.
It remains to scale these projects up. “This is a crucial point of this drought initiative. This is a five-year phase of testing and experimentation, not a program to solve the problem tomorrow.”shade Lamine Ighil Ameur.
Other points to adapt to the RGA
If the search for a solution is a key step in adapting to the RGA phenomenon, the effort must also be focused on prevention. “The important thing is to anticipate the risks of cracks in houses, and that requires information”, he gauges. The first steps have already been taken, notably in 2018 with the Elan law: to build on new land, the builder is now obliged to carry out a soil study, to estimate the risks of the land.
And for the already existing building, “the buyer must systematically be made aware of the RGA risk which weighs on the area, and a document on the subject is now annexed to the deed of sale”, explains Marthe Mouzay, notary in Loir-et-Cher. An approach based on data from Georisks, a government digital tool responsible for identifying low, medium and high risk geological zones.
“Very positive first steps, but which are not yet sufficient”, however, believes Lamine Ighil Ameur. For the researcher, it is also necessary to invest in carrying out an individual diagnosis on the houses being the subject of a transaction, an essential condition to best anticipate the slightest risk. And of course continue to bring the subject into the public sphere: “The French must realize that the RGA is a real natural disaster, even if the damage is not as immediate as that of a flood. »
——
Difficult compensation
If cracks due to shrinkage-swelling of clays (RGA) exasperate the inhabitants, compensation procedures annoy them. A compensation scheme for natural disasters, Cat-Nat, has existed since 1982. But to be considered a victim of ” drought “the criteria to be met by municipalities are particularly restrictive.
A study by the Mission Natural Risks association estimates that nearly 300,000 cracked houses are deprived of compensation each year. However, awareness on the subject is underway. On April 6, 2023, the National Assembly adopted a bill, responsible for better compensating residents who are victims of an RGA.
#Cracked #houses #insurance #companies #solutions