RGA and the Courts: what case law says about 'Adequate Causation'

Understanding 'Adequate Causation' in the face of RGA cracks

Clay shrink-swell subsidence (RGA) is a complex phenomenon where alternating drought and soil rehydration causes ground movement that weakens home foundations, leading to cracks. Faced with this damage, compensating victims is often an uphill battle, particularly when the natural disaster (Cat-Nat) scheme is insufficient or refused. It's in this context that the courts are increasingly called upon, and their recent rulings shed light on a fundamental legal principle: 'adequate causation'.

'Adequate causation' is a legal theory aimed at determining whether a given event can be considered the legal cause of damage. Unlike 'exclusive causation', which would require drought to be the sole cause of the cracks — an almost impossible condition to prove for RGA, often influenced by other factors like foundation quality or nearby trees — 'adequate causation' is more nuanced. It states that drought must have played a predominant role, without necessarily being the only factor, in causing the damage. This pragmatic approach was adopted by courts such as the Poitiers judicial court (June 9, 2026) and the Valence court (May 12, 2026), in shrink-swell subsidence cases involving several concurrent factors.

Damages recognized and covered by the courts

The rulings handed down by the Poitiers and Valence courts detail the heads of damage the judges examined in these cases.

More specifically, the courts examined several items: G5 geotechnical studies, structural repair works, relocation costs, and indexing according to the BT01 index. These elements illustrate the technical nature of RGA cases brought before the courts, without prejudging the outcome of any future case.

What these rulings show about the nature of RGA cases

These recent rulings help clarify the framework within which RGA cases are handled by the courts. They show that the judicial path exists alongside the Cat-Nat scheme — each case still being assessed on its own merits by the competent courts.

In these cases, the courts placed particular importance on the quality of the technical evidence provided by the parties, notably the geotechnical diagnosis and independent expert assessment — factors among others, specific to each case.

The connection with TerraStab

These court rulings highlight the importance of a rigorous geotechnical diagnosis and documented monitoring of soil water conditions. TerraStab produces this type of technical data: soil moisture measurements and RGA risk diagnosis. This information constitutes technical elements that can help document a situation; whether it is taken into account in legal proceedings or compensation is a matter exclusively for experts, insurers and the competent authorities.

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