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More than 16 million homes across France will within 25 years be at risk of damage - often structural - due to droughts, a new study claims, as climate change increases the impact of clay

soil shrinkage on properties.

Data from the Institut de l'économie pour le climat (I4CE) estimates that around 10 million homes are currently at risk of damage caused by droughts.

Homes built on clay soils are at risk of retrait-gonflement d'argile (RGA), a phenomenon where clay soils shrink in droughts and then expand quickly during rainfall. This type of soil is

widespread in France.

It can cause cracks to appear in walls and even building foundations.

However, the I4CE estimates that by 2050, 16.2 million homes will be affected as more and more areas of France experience hotter and drier summers.

In addition, it is leading to an increase in the number of homeowners submitting insurance claims over the damage, driving up premiums and creating a ticking time bomb for the insurance

industry.

Read more: Second-home owners in France could soon face insurance surcharge

“The increase in drought linked to climate change has a direct influence on the RGA phenomenon. Between 1989 and today, the number of recognised claims has risen by 145% in France", says

Sylvain Trottier, director of the association Conséquences, which studies the effects of climate change in France.

“Until now, losses were only recorded in Nouvelle-Aquitaine, Centre Val-de-Loire, Occitanie and the Paca region. Today, we can see the phenomenon spreading to other regions. For example, in

the Grand-Est, Bourgogne-Franche-Comté and Auvergne-Rhône-Alpes,” he added. 

Currently, only properties in Brittany and Normandy are unaffected, as the soil content has less clay than elsewhere in France. 

In light of the potential risks – and the desire for homeowners, insurers, and construction firms alike to take preventative measures before damage becomes severe – tools are becoming

available to help see if properties may be affected.

A map by risk assessment start-up Callendar allows property owners to enter information about their home, to see if it will be at risk of damage from RGA. 

It looks at three main factors relating to the property – the nature of the local soil (including its clay content), structural information about the building, and the risk of drought in the

area. 

It will then tell you whether your property is at low, medium, or high risk of damage.

Perhaps surprisingly, it is homes built after 1960 that are the most at risk, because these are less likely to have basements and underground spaces, meaning structural foundations are less

anchored within the soil and are only present at a base level. 

Damage from RGA can only currently be compensated after the declaration of a natural disaster in the affected commune, although there are plans to attempt to make the claiming process

easier. 

Read more: France’s ‘catastrophe naturelle’ insurance system: how to claim

Earlier this week, 84 communes were declared natural disaster zones for droughts in 2022 and 2023.