A real disaster: more than 90% of houses in these 38 cities are at risk of cracking

The phenomenon of cracks in houses is expected to increase in the coming years and certain municipalities are particularly at risk.

It's a growing phenomenon that's a concern for both homeowners and professionals. Cracks are becoming increasingly common not only on facades but also inside houses and apartments. For residents, it's a worry that their homes are deteriorating; for insurers, it's a worry that they'll have to pay for particularly costly repairs. Especially since the situation isn't going to improve over the years.

According to public data collected by Linternaute , the situation in 38 cities is particularly alarming. Indeed, in these municipalities, at least 90% of the territory is affected by a high risk of building cracks. This data corroborates a projection made in 2021 by France Assureurs, the insurers' federation that brings together 247 companies.

This cracking phenomenon is called "clay shrinkage-swell" (CSH). It involves clay soils that swell in the presence of water—usually in the fall and winter—then shrink during droughts, mainly in the summer. These changes cause soil movements that cause damage to homes, including cracks, due to shifting foundations. Not all parts of the country are affected because the soils are not clayey everywhere.

Currently, 38 towns are most exposed to the RGA phenomenon. More than half are located in Haute-Garonne and the surrounding departments, and a portion is on the Côte d'Azur. But not only that. In total, this represents 515,000 inhabitants. Here is the list of the municipalities most exposed to level 3 of clay shrinkage-swelling, i.e., the highest risk:

• Aniche: 91.72% of the municipal territory exposed to level 3 of the RGA
• Apt: 93.52%
• Also: 99.99%
• Balma: 99.99%
• Good Encounter: 90.08%
• Castanet-Tolosan: 94.39%
• Castelginest: 100.00%
• Caussade: 99.26%
• Condom: 99.51%
• Coubron: 92.44%
• Escalquens: 95.94%
• Esvres: 95.90%
• Fontenay-sous-Bois: 91.33%
• Foulayronnes: 98.01%
• Gardanne: 94.83%
• Gignac-la-Nerthe: 99.50%
• The Verrière: 99.87%
• Pré-Saint-Gervais: 92.60%
• Les Ulis: 99.74%
• L'Isle-Jourdain: 99.75%
• Montfermeil: 98.98%
• Nandy: 97.62%
• Noisy-le-Sec: 90.82%
• Ormesson-sur-Marne: 99.99%
• Port-de-Bouc: 90.01%
• Pulnoy: 96.66%
• Quint-Fonsegrives: 98.26%
• Ramonville-Saint-Agne: 99.37%
• Revel: 93.11%
• Rognac: 97.17%
• Rousset: 99.10%
• Saint-André-de-Cubzac: 90.85%
• Saint-Jean: 99.99%
• Saint-Orens-de-Gameville: 98.18%
• Seals: 94.07%
• Seichamps: 94.88%
• Vaujours: 90.52%
• Velaux: 97.09%

This trend is expected to intensify, as France Assureurs' analysis has highlighted the five departments that are expected to account for 66% of the increase in claims related to the RGA phenomenon by 2050. These are Haute-Garonne, Gironde, Bouches-du-Rhône, Tarn-et-Garonne, and Tarn.