Generally speaking, formal authorisation are required when you undertake new construction work or renovation work to an existing building.
Two main authorisations currently exist as a matter of French Law:1. Permis de construire (planning permission) :

This is required for the main major works undertaken over a property of for a new building.

The intervention of an architect may be also required under specific circumstances.

2. Déclaration préalable de travaux (work declaration) :

Such a declaration would notably be necessary for:

  • A garage or adding an outter building (“dépendance” in French) if the surface is less than 20 square metres;
  • The construction of a wall of more than 2 m in height;
  • Some swimming-pools;
  • Work modifying the external aspect of the building; etc

For further information on French construction law please click here.