Small improvements, which don’t alter the use of the building, only require a déclaration de travaux. This would include improvements such as adding internal walls, skylights, replacement windows and doors, installation of outbuildings such as garden sheds, greenhouses, conservatories, and additions of less than 20sq m m floor space. Open-air swimming pools are also covered by a déclaration de travaux.
 
 
The paperwork is available from the Mairie, the waiting period for approval is about a month and the notice must be displayed for at least two months, (and during the whole construction period if longer than 2 months) with the note "absence d'opposition" (no disagreement).