A preventative archaeological study was carried out for the Centre des Monuments Nationaux (Paris), prior to the restoration of the Preuses wing of the Château de Coucy (Aisne), in 2013. During this study of the building, orthophotomaps of each elevation, as well as the layout plan of the building, were generated from lasergrammetric surveys. These graphic documents were used / will be used as a layout for the consolidation work in the conservation of the wing. This study made it possible to collate hundreds of pictures of the facing and examine the restoration records kept at the Médiathèque de l’Architecture et du Patrimoine (Paris). The comparison of these unpublished data have led to the proposed analysis of the wing by considering each phase of construction – including restoration work – not as successive episodes in the history of the monument, but as entities with strong interactions, on which the renewal of archaeological analysis depends.