Context
Once a working-class quarter of craft and small-scale industry, Paris's 11th arrondissement is now a lively, mixed-income neighborhood dense with collective housing and public amenities. Its proximity to Père Lachaise Cemetery and several local gardens gives it a green character that is unusual for central Paris and central to the quality of life there.

The site comprises three former ENEDIS buildings, Nation 1, 2 and 3. While Nation 2 and 3 remain in ENEDIS use, Nation 1 has been returned to the City of Paris and is the exclusive subject of this building permit.

Heritage
Built in 1929 to an Art Deco "standard model" designed by Alsatian architect Paul Friesé and adapted by Paul Marozeau, Nation 1 belongs to a generation of interwar substations built in reinforced concrete. The building pairs a front administrative wing facing the boulevard with a rear technical wing, divided by a full-height central nave lit from above by a concrete lantern set with translucent glass blocks. Symmetrical upper floors, linked by walkways and twin metal staircases, organize vertical circulation around this luminous void. The building was extended in 1949 and 1957, and modernized in 1979 by architect Darsonval.

Concept
The design process began with a diagnostic reading of the existing structure before any architectural gesture was proposed. Four qualities of the building were identified as its essential DNA and became the foundations of the project:

Material / a massive, thick, reinforced-concrete volume, emblematic of 20th-century industrial architecture.
Volume / an architecture of emptiness rather than mass, organized around a nave more than 20 meters tall.
Light / the unifying element that animates the voids and defines the building's atmosphere.
Function / a rational, engineer-designed building: offices at the front, industrial infrastructure at the rear, a "machine building" that served the city.
The intervention is conceived as a continuation of this story rather than a rupture: preserving the existing structure and embodied carbon wherever possible, introducing bio-based materials and dry, mixed-metal construction for new additions, and relocating and reusing existing staircases for new circulation and mezzanines.

Two architectural gestures activate the building. The historic nave becomes a light cleft running from roof to basement, its daylight bouncing off the superstructure walkways and reaching down to bring the basements out of darkness and into daily use. A planted green roof extends this gesture skyward, with vegetated walkways along the nave.

This cleft also generates programmatic and urban permeability: every layer of the program is visible from the entrance, and an interior street draws the city of Paris directly into the building.

Façades
The existing front/rear duality is preserved in the facades. The "noble" front elevation on Boulevard de Charonne and its two lateral returns will be restored to their original color, texture and joinery, with new anthracite-grey steel frames meeting contemporary thermal standards while retaining the building's industrial finesse. Demolitions are limited to restoring the original symmetry and solid/void relationships, rooftop additions are recessed to minimize their visual impact, and all new glazing is kept clear and discreet to foreground the heritage fabric.

Program
Murmure will house workspace and retail dedicated to sound and music:

- Coworking office space in the superstructure, with walkways opening onto the nave for natural ventilation
- Ground-floor shops and a restaurant along a naturally lit, 25-meter-high interior street
- Recording studios and rehearsal/teaching rooms in the basement levels
- A landscaped rooftop terrace with medium-sized trees, for both occupants and occasional public access
- A technical basement (R-3) housing ventilation and smoke-extraction plant for the studios
Acoustic performance was a defining constraint throughout: vibration measurements addressed metro-induced noise in the basement studios, while office floors were engineered for reverberation control, impact-noise reduction and inter-level isolation.

Construction
The rehabilitation combines major substructure and superstructure works while maintaining the stability of the existing building — a complex sequence phased from strip-out through structural completion:

- Sept 2023 / service order for studies and site installation; strip-out works begin
- Oct 2023 / basement access ramp completed
- Nov 2023 / construction works service order issued; temporary shoring, façade retention and superstructure bracing put in place
- Dec 2023 – Feb 2024 / early substructure works
- Mar 2024 – Jan 2025 / tower crane in operation on site
- Feb 2024 – Jan 2025 / main underpinning and excavation works, deepening the existing basement by a further 6 m (from –5 m to –11 m relative to the boulevard) and removing roughly 10,000 m³ of soil

Underpinning proceeded column by column, each requiring about a month of work, through temporary concrete pads and steel transfer beams, permanent transfer beams cast at a height of roughly 1.40 m, and sheeted underpinning pits excavated in three successive stages before new permanent footings were poured.

Studio A, designed for a 7-meter clear ceiling height, required the removal of existing columns and beams via new megabeams beneath the ground-floor slab, deepened peripheral walls, and a full "box-in-box" acoustic isolation system on spring supports to protect against metro vibration.