Floods, risks of submersion, drought… The impacts of global warming are already visible in France. A report published at the end of May by the Conséquences association focuses on one of them: clay shrinkage-swelling (RGA). A phenomenon that is the cause of cracks appearing on houses. And for good reason: when the clay soil on which houses were built swells in winter when it rains and shrinks in summer during droughts, the entire structure of the house is weakened. When they are repeated, these variations in soil humidity cause houses to move over time and cause cracks on the facades.The increase in droughts linked to climate change directly influences the RGA phenomenon. Between 1989 and today, the number of recognized claims has increased by 145% in France“, indicates Sylvain Trottier, director of the association.
What worries climatologists is that since the 2000s, the phenomenon of clay shrinkage and swelling has spread to new regions.Until now, disasters were only recorded in New Aquitaine, Center Val-de-Loire, Occitanie and the PACA region. Today, we are seeing a spread of the phenomenon to other regions. For example in the Grand-Est, in Burgundy-Franche-Comté and in Auvergne-Rhône-Alpes, where the increase in claims is spectacular“, explains Sylvain Trottier.
No region is now spared, with the exception of Brittany and Normandy, where the soil is less clayey and the differences in humidity between seasons are less pronounced. According to data from the Central Reinsurance Fund (CCR), aggregated in the report by the Conséquences association, more than 20 million French people are exposed to this risk. The Institute for Climate Economics (I4CE) estimates that 16.2 million homes are likely to be cracked by 2050 (compared to 10 million likely to be cracked today). To carry out this projection, the I4CE is based on the government’s reference scenario (in this case that of the IPCC), which predicts in particular an increase in temperatures of 2.7 degrees by 2100.
To find out if your house is likely to be affected by the clay shrinkage-swelling phenomenon, you can consult the site “Home Climate Risk RGA“, developed by the start-up Callendar, which specializes in assessing climate risks. The latter allows French people to get an idea of the level of risk to which their home is exposed, simply by entering their postal address into the tool and providing some characteristics of their house (collective, individual, presence or absence of a basement, shape of the building, etc.).
To make its diagnosis, the tool cross-references three factors – the nature of the soil, the structure of the building and the climatic risk (drought) – and deduces the level of vulnerability of a house: low, medium or high.All houses are likely to be affected. However, single-family homes built after the 1960s are the most vulnerable. Particularly those that are not anchored to the ground, i.e. that do not have a basement or crawl space,” concludes Sylvain Trottier.
