FREAKS freearchitects answered an add from a private client wishing to build an extension on the roof of an existing building in Saint-Ouen (northern neighbourhood of Paris).
It actually was not about an extension but the aim was to welcome a new neighbour to be installed on the roof of the client house. The project had to deal with the existing configuration of the building where the client and his family were living (and where they were still leaving during the time of the building process).
The client decided to build the whole project on his own. So we proposed to go for an construction process easy to manipulate based on wood particles and prefabricated (Finn Forest®).
Details and materials are basic so then the building process did not took too long and the new neighbour family was able to arrive within the expected schedule.
Self-construction in addition with basic materials explain why the total amount of budget ended so low and was very competitive within the Parisian context.