Movable curtains of translucent PVC mesh cover the facade of this block of offices and flats in Paris, which has been converted from a 1970s concrete structure by local practice Moussafir Architectes.

The practice collaborated with Amsterdam-based design studio Inside Outside on the 10-metre-high curtain facade, introduced to complement the original building's concrete structure, which has been stripped back to create a "brutalist aesthetic".

"The principal quality of the original construction resided in its neutral and generic character," explained the studio.

"It is this overall grasp of the building's structure that guided our architectural choice, from the insertion of interior elements (staircases, guardrails, floor, and ceiling coverings) to the design of the envelope," it continued.

Across its ten floors, the existing building has been divided into four storeys of workspaces and four floors of flats, including a two-storey penthouse.

The basement and ground floor contains a series of showroom spaces illuminated by circular skylights, with an office space occupying the first floor above overlooking a small courtyard at the rear of the site.

Across all of these levels, the stripped-back concrete columns of the existing structure frame rough masonry walls, with the office given a warmer feel with wooden floors and ceiling panels.

Inside the flats, a similar interior treatment has been used, with the exposed concrete of the 1970s building complemented by white walls, metal window frames and simple partition walls.

At the top of the building, the two-storey penthouse is topped by a mansard roof, the exposed concrete frame of which defines the top floor library area, with skylit window boxes created in between the large supports.

"Our decision to expose the structure provided the incentive to not differentiate the dwelling spaces from the offices and to design the flats like offices," explained the studio.

Each level of the upper storey is sheltered by a row of motorised curtains on the exterior of the main facade, which have been perforated to create a pattern of a tree when all of them are closed.

"The curtain's undulating movement can be controlled on each floor as well as the lighting effects across the entire surface of the PVC mesh thanks to the discrete integration of LEDS," said the studio.

"Circular perforations define the outline of a tree, rendering the mesh permeable to the wind while also casting playful swathes of natural light into the interior," it continued.

Moussafir Architectes was founded by Jacques Moussafir and is based in Paris. Previous projects by the practice include a geometric, cubist-influence home in Paris, and a concert hall in Tours finished with a quilt-like material.

The photography is by Hervé Abbadie unless stated.