ArcelorMittal steel transforms the Bois-le-Prêtre apartment tower in Paris

Detailed information

Rehabilitation and transformation project for social housing

The 50-metre tower with a total of 96 social housing units distributed over 16 floors was built in 1962. Due to the fact that over the years the building had become obsolete in regards to technical issues as well as living conditions, the owner of the building, Paris Habitat, initially considered a complete demolition in 2006.

This plan was abandoned in favour of an exhaustive transformation project that included an expansion of the apartments by the expansion of the floor construction on all four sides of the tower. This way, the space in the living rooms could be increased, winter gardens and balconies could be created, and surface area was gained.

Thanks to these measures, living comfort, natural light, and the view from the apartments was improved, and energy consumption (especially regarding heating) was reduced significantly.

The unique aspect of this transformation project was the fact that the residents could actually stay inside the building while the construction works were going on.

Parisian architects Frédéric Druot, Anne Lacaton, and Jean Philippe Vassal developed the plan for this rehabilitation and transformation project.

The project began in 2005, a number of years before completion, but all of the involved parties agreed that it was worth the time as it was conducted in collaboration with the residents and concerned the long-term improvement of the living conditions.

Steps & results of the rehabilitation and transformation project

• Reconfiguration of the lobby - it was set on the street level.
• Installation of two new elevators to facilitate people flow on all floors.
• On the floors, additional space was created for larger living rooms and kitchens or additional bedrooms and bathrooms. In total, an additional 3500 m2 was gained.
• The highlight was the creation of glazed winter gardens and balconies on the east and west facade. With dimensions of 2 m long and 1 m wide, they permit natural light to enter the apartments.
• Four new apartments were created.
• Seven different types of apartments (instead of three different types before the transformation) for families of different sizes are now available.
• In addition to thermal insulation, the new facade and winter gardens also protect the building from outside noise (coming from the ring road).

Although the residents would experience a slight increase in rent over the following years, this cost was offset by a 50% reduction in energy consumption.

Use of metallic coated steel

ArcelorMittal's metallic coated steel played an important role in the new aesthetics of this housing tower - in the interior as well as the exterior. In the interior, the same material was used for the ceilings of the winter gardens and partition walls.

Thanks to the high light reflectivity of this metallic coating, the Tour Bois-le-Prêtre glistens in the sunlight and makes it stand out from its surroundings. The silver-metallic sparkle will be maintained for a long time thanks to the thin layer of aluminium oxide on the surface of the coating.

This steel also contributes to the fire protection of the steel columns in the exterior – it was used for the outer skin of the column envelope, with a mineral wool insulation core guaranteeing a protection REI 90 minutes. The solution employed is based on the innovative firestop solution patented by ArcelorMittal and developed in collaboration with the company SDI (Synergy and Industrial Development) located in Lorraine.