PRESS RELEASE

15 February 2022

COMMUNICATION TO THE NATIONAL ASSEMBLY PUBLIC POLICY EVALUATION AND AUDIT

COMMITTEE

CLAY SOILS AND NATURAL DISASTERS

Sharply increasing damage and an unsuitable prevention and

compensation regime

The shrinkage-swelling of clay soils, or the shrink-swell phenomenon, consists of a series of

movements caused by variations in the water content of clay soils. Known in France for more

than 30 years, it has damaging consequences for housing that give rise to compensation,

included since 1989 in the natural disaster regime, known as “Cat Nat”. This phenomenon

has attracted recent attention from the public authorities due to the growing magnitude of

the risk and the related claims and also because of the increase in dissatisfaction expressed

by the exposed populations. Referred to by the National Assembly Public Policy Evaluation

and Audit Committee concerning the prevention and compensation of damage caused by

the shrink-swell phenomenon, the Court of Accounts conducted an investigation taking into

account the history of the issue and above all, more recent parliamentary and

administrative work. The report that is being published today shows that as the

phenomenon is evolving, its management is increasingly being called into question. In view

of this situation, the Court recommends promoting preventive measures and reconsidering

the compensation regime.

A long-standing phenomenon, with compensation included in the natural disaster regime

The shrink-swell phenomenon is the result of the combination of a geotechnical situation and

a series of climatic episodes: on certain clay soils, a series of wetting periods and drying

periods can cause damage to buildings. The Court notes that the implementation of

preventive measures was delayed and remains insufficient today. Knowledge of the

phenomenon, although long-standing, was not accompanied by any effective prevention

policy until the entry into force of the French Act of 23 November 2018, known as the ÉLAN

Act, which set out construction rules for high-risk areas.

A foreseeable increase in the shrink-swell phenomenon, with an increasingly contested

management strategy

Taking into account the reasoning and recommendations formulated last March by the

General Council for the Environment and Sustainable Development (CGEDD), the General

Inspectorate of Finance (IGF) and the General Administration Inspectorate (IGA), the Court

analysed the strengths and weaknesses of the compensation regime. Integrated into the

natural disaster regime, the current rules would be sustainable if the damage caused by the

shrinkage-swelling of clay soils was, in the medium term, constant in terms of its frequency,

severity and financial impact. However, the extent of the effects of climate change and the

various forecasts and projections made, in particular by the french public reinsurance group

(CCR) and the French Insurance Federation (FFA), show that this is not the case. Indeed, since

1989, the shrinkage-swelling of clay soils has accounted for 36% of the claims observed for

natural disasters and half of the most expensive events recorded over the same period.

Originally limited to certain regions, it now affects all areas of metropolitan France and more

than half of the stock of single-family homes. All of the studies undertaken recognise that the

costs associated with the shrink-swell phenomenon will increase sharply over the next 30

years.

A more appropriate prevention and compensation system is needed

Based on the natural disaster regime, the compensation mechanism for damage linked to the

shrink-swell phenomenon is currently reaching its limits and should lead the public authorities

to question its very classification as a natural disaster. The spread of the phenomenon across

metropolitan France, its intensity and its social and financial consequences require that the

responses provided by the public authorities be adapted. In this report, the Court’s

recommendations focus on informing purchasers of potentially exposed properties,

monitoring the effective implementation of the construction provisions in the Élan Act and,

for buildings built before 2020, developing research into effective remedial measures. The

Court believes that if compensation continues to fall under the natural disaster regime,

significant changes will need to be considered, following thorough impact assessments.

Read the report

PRESS CONTACTS:

Emmanuel Kessler

◼

Head of Communications

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Tel.

01 42 98 55 62

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emmanuel.kessler@ccomptes.f

Julie Poissier

◼

Head of press relations

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Tel.

01 42 98 97 43

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julie.poissier@ccomptes.f

@Courdescomptes

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