The new clay shrinkage-swelling (RGA) exposure zoning

A new clay removal and swelling (RGA) exposure zoning will apply from July 1, 2026: to promises of sale or authentic deeds of sale of unbuilt building land and contracts for the construction of single-family homes.

A new map

To take into account the high loss rate of recent years and in particular the effects of climate change, the order of 9 january 2026 Updates the 2020 Clay Retraction-Swelling (RGA) Exposure Map.

This update leads to an increase in the medium and high exposure areas, i.e. those subject to the provisions of the law Élan : they now represent 55% of France’s territory, up from 48% in 2020.

Check out the new interactive map updated on Georisks.

What is the phenomenon of shrinkage-swelling?

Surface clay soils may vary in volume as a result of changes in their water content, due to weather conditions.

They retract during periods of drought (phenomenon of “withdrawal”) and swell when the rains return (phenomenon of “swelling”).

These variations are slow, but they can reach a large enough amplitude to damage the buildings located on these grounds.

To inform you and better protect you, consult the dossier on clay shrinkage and swelling on the Georisks website.