UFO - Headquarter Leboncoin Group, a workplace that respect the context

In the 19th century, the Sentier neighbourhood became known as a textile hub specializing in woven fabric, an historic association that is reflected in the building’s façade with its weft and warp of horizontal and vertical lines.
This new building envelope brings out the building’s intrinsic qualities, transforming it into a modern workplace that acknowledges the urban context while respecting its original form. It also allows light and air to break up the rather monolithic aspect of the block, allowing glimpses of interior spaces and greenery.
Floor area in the renovated building is around 10% greater than before: this was achieved by reorganizing the ground floor and by adding a mezzanine level on the final storey. At ground level, the building’s base has been freed up through the creation of a double-height double-aspect hall, which ensures a certain visual porosity in the neighbourhood, particularly in the rue des Jeuneurs, where the new main entrance will be located.
The building’s courtyard has become a patio garden laid out in cascading terraces, with a planted wall that rises almost 7 m. All the courtyard façades are entirely glazed, allowing the building’s green beating heart to be enjoyed from inside.
To open up the building to the exterior and provide light and air to users, a terrace has been created on the second level and the original technical roof has been planted.
UFO’s courtyard has become a quiet green oasis whose patio and terraces offer a calm place to breathe in the hustle and bustle of the Sentier.

For Axel Schoenert architectes, the main challenge was to revamp the building’s image. Inspired by brutalism, the three original street façades featured massive prefabricated-concrete mullions and transoms. These 1970s features were removed, and in their stead a curtain wall erected that ensures 21st-century standards of insulation and natural-light penetration. Constructed from gold-tinted anodized-aluminium chassis, and equipped with motorized white blinds, the curtain wall is clad with slender prefabricated white-concrete frames. With its strong horizontals and verticals, this new façade is reminiscent of the looms that were so common to the neighbourhood in the 19th century.

Not only are the panels self-cleaning, they also reduce the production of carbon dioxide by reacting with sunlight, a property that makes them unique in this very urban context. The play of depth and proportion brings a certain lightness to the façade that makes it appear to soar towards the sky.

Measuring 3.20 m high and 4.68 m wide, the white-concrete frames on the street façades feature very fine edges, which vary from 6 cm thick on the second storey to 30 cm thick on the sixth. Special moulds were needed to produce them, and although they were initially intended to be in high-performance fibre-reinforced concrete, traditional concrete was used in the end, requiring precise calculations with respect to the rebars, the thickness between the rebars and the surface, as well as precise modelling of each part so as to ensure correct edge dimensions within a tolerance of only 2 cm. A prototype was made in February 2019, after which several months’ development were needed before production could go ahead. The 200 frames, which reinterpret and modernize the brutalist aesthetic of the original street façades, weigh 3 tons each, meaning that a suitable fixing system had to be devised. To ensure perfect alignment across the entire expanse of the façade, stainless-steel fixing rods were used which allow adjustment in three dimensions (depth, height and width) and transfer the load to the façade.

The large metal box on the final two floors is suspended from the building’s concrete frame. Cantilevered 1.40 m out from the façade, this two-storey box required special handling: a concrete beam, 280 x 700 mm in section, runs parallel to the façade and bears the box’s full load. Attached to the steel frame, vertical truss rods support the sheet-metal floor, sealed into the original building’s concrete frame. All of this is invisible from the courtyard: visitors see only steel chassis containing three glass panes measuring 2.80 m wide by almost 6 m high which are held in place by glazing beading.

The courtyard façade
The brand-new all-glass courtyard façade is characterized by its light and transparency as well as by the five projecting boxes that animate its surface and allow exceptional views onto both the building and the patio. On the final two floors, a sixth metal box stands out through its exceptional dimensions. In place of the thick concrete slabs that formerly clad the lower sills, we now find 2.70-m-high glued glazing panels. Half of the modules can automatically open 5 cm towards the exterior, parallel to the façade, thanks to a system of pantograph mechanisms which allow for natural ventilation and smoke evacuation, all the while forming a guard rail.

For UFO, Axel Schoenert architectes developed an ambitious and effective architectural and office solution that can adapt to the evolution of the workplace as well as fulfilling user expectations and client requirements. With a capacity of 1,000 people, UFO was designed to achieve exceptional environmental performance and has been certified under five standards: HQE EXCELLENT, BBC, BREEAM EXCELLENT, WELL GOLD, WIRED SCORE GOLD. The building is thus perfectly in tune with current environmental challenges and is intended to set an example. Today UFO is the headquarters of the Leboncoin group.