As climate change increasingly disrupts weather cycles, ADEME launched a call for projects in November 2023, as part of the “France 2030” investment plan. His goal? Adapt buildings to climate change and identify solutions to act on the disorders caused by several phenomena. One of them is worrying more and more climatologists and, by ripple effect, all construction professionals. This results from a reaction of certain clay minerals present in the soil.
Depending on the water content of the land, the latter can vary in volume: shrink during periods of drought or swell when the land is again saturated with water, for example in the fall. The repetition of these variations in humidity in the ground is likely to cause houses to move over time. This process does not constitute a major risk for the population, but “it causes damage to the structure of buildings, such as cracking of walls and floors“, indicates the General Commission for Sustainable Development (CGDD).
This phenomenon is that of clay shrinkage-swelling (RGA). “The increase in droughts linked to climate change directly influences the RGA phenomenon“, assures Sylvain Trottier, director of the Conséquences association, which published a report on the subject in May 2024. According to data from the CGDD, “which emanate in particular from those of the Geological and Mining Research Bureau (BRGM)“, according to Sylvain Trottier, 10.4 million individual houses are moderately or strongly exposed to RGA. That is 54% of individual housing. More than 4 million houses would even be very exposed. This risk mainly affects individual houses with structures light, with shallow foundations, without basement or crawl space According to CGDD data, housing built after 1976 records the greatest number of losses. This is the typology. of property – considered more vulnerable to this hazard – which must be the subject of great vigilance on the part of potential property buyers Even if the damage caused by these movements of land is now compensable under natural disasters, indicates the. CGDD.
To find out the level of risk to which the property is exposed, future buyers can enter the address of the building on the Risque Maison Climat RGA site, developed by Calendar, specializing in the assessment of climate risks. It is all the more important to anticipate this risk.”that no region is now spared, with the exception of Brittany and Normandy, where the soil is less clayey“, indicates Sylvain Trottier. Some, however, are more affected than others: this is the case of New Aquitaine, Occitanie, Center-Val de Loire. “These three regions represent more than half of the metropolitan areas exposed to high or medium hazard.“, indicates the CGDD. The large urban centers in the Paris region or in Hauts-de-France, where there is a very high density of individual houses, are also extremely vulnerable. In these areas, cracks in the ground and property facades are likely to appear.
