Built in the 1960s by Raymond López, the Bois-le-Prêtre Tower is part of a group of high-rise apartments rising by the north ringroad of Paris. Their radical transformation is set forth as an alternative to the demolition-reconstruction policy initiated by the French government in 2003, and affecting the large residential blocks in the city. This approach offers an opportunity to show that a refurbishment operation is cheaper, quicker and has a better capacity to produce a regenerating effect than a tabula rasa operation (the refurbishing cost is significantly lower).

The existing tower houses 96 social housing units for use on a rental basis. The building system, consisting of concrete slabs and shear walls, and of independent facades, has a great transformation potential. Without altering the original structure and without having to ask residents to temporarily vacate their homes, a double operable skin is installed little by little, and this skin extends the interior space three meters along the entire perimeter of the building, creating a new living space that reduces energy use by 50% and improves sunning and living conditions inside the dwellings.