House cracking threat spreads to new areas in France, putting 12 million properties at risk

Properties in more than half of mainland France (55%) have been classified as being at medium or high risk of cracking from clay subsidence, according to a new map approved by the environment ministry – up from 48% previously.

The map, which replaces one drawn up in 2020, could make it easier for affected homeowners to access support through France’s unique catastrophe naturelle insurance fund. It affects more than 12 million homes.

Most of the newly affected territories are in Auvergne-Rhône-Alpes, Bourgogne-Franche-Comté, Grand Est and Centre-Val de Loire – but they are spread across the country.

Cracks from subsidence appear as the clay soil beneath houses shrinks during droughts and then expands again when it rains.

Houses built of concrete blocks since the 1970s are particularly at risk, as nationwide standards introduced at the time allowed for smaller and shallower foundations than those now required to protect houses from clay subsidence.

Stricter standards were put in place in 2024. Advertisements for homes put up for sale must now warn of geological risks. As well as clay subsidence, this can include threats such as earthquakes and flooding. 

Most listings simply refer buyers to the government site Georisques. 

These risks must also be mentioned in property sale documents.

A drought in 2023 – when a dry winter was followed by a heatwave – led to far more cases of cracking than previously recorded and brought the issue into the media spotlight.

Affected communes can apply to be declared a catastrophe naturelle area, unlocking a dedicated insurance fund to help cover repair costs.

Claims for clay subsidence cracks are subject to a higher franchise (excess) of €1,520 compared to €380 for other claims under the catastrophe naturelle scheme.

However, the isolated nature of the damage – with some homes developing cracks while neighbouring properties are unaffected – and the difficulty of proving a link between weather conditions and cracks appearing months later have left some homeowners struggling to claim.

In the most severe cases, the structural integrity of walls can be compromised, forcing residents to leave their homes until repairs are completed.

At the moment, the government is experimenting in 11 departments with a revenue-based grant system to help people repair properties with cracked walls, with maximum grants of €15,000 available.

The departments are: Allier, Alpes-de-Haute-Provence, Dordogne, Gers, Indre, Lot-et-Garonne, Meurthe-et-Moselle, Nord, Puy-de-Dôme, Tarn and Tarn-et-Garonne.