The building is governed by operating constraints that the project strives to respect: it is a utilitarian structure, a machine that must work perfectly.

The fire-stop levels and the risks of explosion lead to relatively closed volumes of a fairly imposing scale given by the sheltered components (TR and SEMC).
We take advantage of these constraints by proposing an architecture that is both massive and delicate and that draws its strength from its materiality.

The interplay of equipment, textures and colours offered by its implementation allows us to create rich and varied surfaces.

The building operates on two scales:

• On an urban or distant scale, it displays a play of large sculpted blocks.
• On a pedestrian scale and in close vision, it acts as a composition of subtly contrasted and worked materials.

On the street side, the volumetry of the building ensures the transition in size between the two adjoining buildings: a main body 12m high is aligned with the building on the square side, while a narrower volume rises to 15m, signifying the entrance and responding to the beautiful brick building on the east side.

On the courtyard side, the building is stepped from the ground floor to the first floor. The mass effect is thus attenuated in favour of the empty space of the courtyard which breathes, more open to the interior of the island. It is not a rear façade. It is the subject of a meticulous treatment, just like the façade on the street, adorned with mashrabiya, which highlights the vertical circulation and conceals the ventilation air intakes.

A 3m high base with a differentiated treatment manages the relationship with the street. The terracotta bricks are a perennial material, able to withstand daily aggressions (washing with water, shocks, etc.). The modenatures of the wall (joints and reliefs) protect it from possible graffiti (graffiti artists prefer smooth surfaces) and from the sticking of posters. This relief also gives depth to the facade by catching the light and generating shadows.
The base is thus directly aimed at the pedestrian.

Horizontal lines of terracotta bricks protruding every meter stratify the building in its height making it very easy to apprehend. They constitute a utilitarian rather than ornamental motif as they protect the lower rows of mud bricks.

The roof, also known as the fifth facade, will be particularly visible from the neighbouring buildings.
It is treated with great care: the technical organs and other ventilation ducts are gathered in a volume that surmounts the TR.

The surfaces are vegetated, thus ensuring better retention of rainwater, improving inertia and promoting biodiversity.

The industrial program of the building offers us the opportunity to create an architecture that composes in two a priori opposite registers.

The first consists in restoring and assuming the technical vocation without trying to disguise the construction as “something else”.

The second proposes a singular materiality and tectonics that allows the Tolbiac station to show benevolence and generosity towards its environment.

Our ambition would be that it would become a “natural” part of the streetscape as soon as it is completed.

We have also sought to create an implicit filiation with the industrial and technical heritage of the first and second generations of industrial buildings that are still very present in Paris, either in their original use or in the context of transformation.

More generally, the materials used are chosen for their quality of appearance, their environmental quality and their robustness.
They are left raw and visible, which gives the project a great constructive realism and a beautiful minerality.

A primary concrete structure provides the infrastructure and the partitioning of the spaces while ensuring compliance with the constraints imposed (in particular mechanical resistance and required fireproofing degree).
On the periphery of this skeleton, adobe brick and terracotta brick walls form the outer envelope.
These walls form a benevolent and eco-responsible protection, with an outstanding quality of appearance.

A singular and unprecedented materiality

The terracotta brick and the raw clay brick write a duet score.

The terracotta brick, which does not fear aggression or water, is used in the base and in the anti-erosion crossing lines.
It protects the raw clay brick, the majority of which is used in the best possible conditions and with a view to durability.

The difference in colours gives a soft polychromy to the facades, which resonates with that of the neighbouring building.
The work of extruding the terracotta bricks completes the polychromy with a set of bas-reliefs that shades the facade in a dynamic and changing manner according to the time of day.

Although it was not really a Parisian material at the beginning, brick is part of Parisian history: at first of modest and cheap connotation, it was mainly used in industrial constructions, social housing (HBM) before extending to other programs and acquiring its letters of nobility. The swimming pool at the Butte aux Cailles, designed by architect Louis Bonnier and located near the site, is a reference in this field.

An architecture of electricity

Our project follows in the wake of Parisian industrial architecture and more specifically the work of Paul Friesé, architect of most of the Parisian electrical substations built at the beginning of the last century.

It is obviously not a question of taking a nostalgic approach, but rather of creating implicit connivance with this rich heritage.

We propose a contemporary and specific reinterpretation, sometimes even imperceptible, of some characteristic elements:

• The organization in plan with the SEMC, the most imposing volume of the programme in a central position, flanked on either side by vertical circulations.
• The large bay on the north side is reminiscent of the large central canopies in the engine rooms. This relatively abstract opening, the only one on the façade, makes the architectural object enigmatic due to its “non-standard” scale. It provides natural, soft and constant northern light without any risk of overheating due to solar gain, which highlights the SEMC by magnifying the concrete framework. The latter is the only element that will be perceptible from the street in a counter-dive. If, however, no visibility is desired, the glazing can be sandblasted, screen-printed or reflective.
• The name of the post appears as a watermark through a set of coloured bricks, in keeping with the tradition of naming the posts and substations that constitute landmarks in the city. The old substations were named after the electricity distribution company to which they belonged (Cie parisienne de distribution d’électricité for most of the substations in Friesé) and sometimes the name of the district they irrigated.

This choice of writing inscribes the building in a history, that of the great narrative of modernity in which the democratisation of electricity played an essential role and continues to do so today, in the age of the “electric city”.