How climate change is weakening our homes

These are terrible images that send shivers down your spine. With 600 liters of rain falling per m² in a few hours, the floods of Valencia in Spain, on the night of October 28 to 29, will go down in history. According to an HEC Paris survey, Viavoice, with Nouvel Observateur, 83% of French people fear serious flooding. All insurers know that their business is being significantly disrupted by climate change. “The impact is an intensification of weather eventsspecifies Ronan Désérable, innovation manager at MAIF, we are going to have alternations of extreme events: repeated heavier rains and alternations of drought.“The equation seems curious, but one degree more, linked to global warming, represents 7% more humidity and therefore more abundant rain.”There are two issues: a mitigation issue, how on a humanity scale, we reduce our carbon emissions because they have an impact on climate change and then in the short term, how we adapt to be less vulnerable to these events.“

Cracks in houses linked to shrinkage-swelling of clays

Flooding and the shrinkage-swelling of clays are the main risks linked to climate change. 54% of homes in France are affected by the risk of drought due to clay soil. A phenomenon which particularly concerns Vienne and Deux-Sèvres. “The soil will expand during periods of rain and will shrink during periods of drought. This will cause micro-movements in the foundations of the house and potentially generate staircase cracks which are quite characteristic.” explains Ronan Désérable. This concerns 10 million houses in France. Obviously, depending on the exact nature of the soil and the construction of the house, the building will be more or less vulnerable. A large building in terms of surface area or a town house will be less sensitive than a pavilion with a garden.Statistics from the Geological and Mining Research Bureau (BRGM) show that houses built after 1976 are more exposed“The Elan law of 2018 requires real estate builders to carry out soil analyzes before any construction.”On the scale of the profession, in particular France Assureur, there is a large-scale experiment with 300 companies to test a few means of prevention and see their effects“, specifies Ronan Désérable.

However, there are ways to limit aggravating factors. “The challenge will be to maintain constant humidity around this house. It is necessary to check that the evacuation of rainwater is done correctly to avoid these variations in soil humidity.“, explains Ronan Désérable. Vegetation planted too close to the home will dry out the foundations. Sensors in the ground allow the humidity level to be assessed. It is possible to have a vulnerability diagnosis established by an expert.

“One in two French people do not know the risks of their home“

What needs to change in France is the culture of risk. Oceanic storms, Mediterranean episodes, and the nature of the soil particularly expose France. “One in two French people do not know the risks around their home” notes Ronan Désérable. It's too little to act upstream. “At the same time, there are almost 8 out of 10 French people who are ready to do more prevention, to have adapted advice“. This is why the Niort-based insurer is offering a new tool accessible to all: AuxAlentours by Maïf. A site which allows, by indicating only its address, access to all the risks linked to housing.

Since 1982, France has implemented the natural disaster regime intended to cover compensation linked to damage caused by floods, shrinkage-swelling of clays (RGA), marine submersion or cyclones. This scheme is financed by the “CatNat surcharge”, a tax on insurance contracts and for the other half by the Central Reinsurance Fund (CCR), which benefits from an unlimited guarantee from the State. A regime envied by other countries of the European Union, but in great demand. “When we look at the figures for natural disasters, between 2010 and 2020, costs have doubled. Since 2020, they have tripled.“What was exceptional is becoming more recurring. Especially since the costs of repairs have increased considerably recently. The contributions of policyholders will inevitably increase. Hence the interest for insurers to encourage preventive actions .

Land use planning also has an impact on the effects of climate change. Soil erosion and runoff is accentuated by intensive agriculture. The disappearance of hedges in the countryside and the waterproofing of soils encourage flooding. Daniel experienced the floods of the Clain in Poitiers in a house, he believes that we must ask ourselves the right questions. “I think we should review everything upstream and not try to put in cofferdams, because the water will be stronger than us.“This requires us to rethink the development of our cities and our landscapes, in consultation with all stakeholders.