Square Root
Square Root draws its identity from the convergence of a structured approach — inspired by the spatial permutations of a Rubik’s Cube — and a sensitive connection to the natural landscape.
The project is based on the rigorous development of an orderly façade grid, set in tension with the site’s inherent qualities. It thus expresses a fundamental conceptual duality between geometric rationality and integration into the landscape.
A neighbourhood in urban renewal
The Terraillon ZAC in Bron forms part of a wide-ranging urban regeneration project launched in 2008, aimed at radically transforming a neighbourhood of large housing complexes dating from the 1960s. This urban area falls within the boundaries of the Bron-Terraillon neighbourhood under the National Urban Regeneration Programme, PNRU, run by the National Agency for Urban Regeneration, ANRU.
Carried out across an area of approximately 6.5 hectares, this regeneration process involved targeted demolition, the redesign of public spaces, and the gradual reconstruction of housing. The aim was to diversify the residential offering and to reintegrate the neighbourhood into its urban environment on a sustainable basis.
Originally designed during the Trente Glorieuses to cope with rapid population growth, the neighbourhood gradually suffered from structural malfunctions: a lack of facilities, inadequate transport links, and a decline in its image.
The urban renewal project now aims to address these weaknesses by offering a more balanced, open, and attractive living environment.
Coming up with a new way of building
The urban project follows a controlled transition approach, balancing contemporary requirements with gradual integration into the existing urban fabric. It is based on several key objectives: reducing the environmental footprint of buildings, promoting energy efficiency, strengthening social diversity, and bringing about a sustainable improvement in residents’ quality of life.
Centred around Rosa Parks urban park, which forms the very backbone of the neighbourhood’s landscape, the proposed design places nature at the heart of the city. It creates densely landscaped block centres, increases the number of green spaces, and limits soil sealing, thereby helping to mitigate the urban heat island effect.
The redevelopment of the road network also opens up the site, promoting clearer circulation patterns and prioritising soft mobility.
Centrally located and offering unobstructed views southwards across the park, the 82-unit development of Square Root forms a key element of the ZAC. It comprises four small-scale buildings, arranged according to the open-block principle. This is designed as a genuine transitional space between the city and the privacy of residential life.
To the north of the site, buildings A and B house social rental accommodation for families, while to the south, buildings C and D, which open directly onto the park, offer social home-ownership accommodation.
By closely integrating the built environment, the landscape, and the ways in which the area is used, Square Root contributes to the creation of a sustainable, inclusive neighbourhood that is fully rooted in its context, offering its residents a peaceful and evolving living environment.
An open block
The 82-unit housing project is organised around the concept of an open block. Careful attention has been paid to the residents’ journey from public space to their homes, with the aim of clearly defining the entrance sequences and creating a gradual transition between communal areas and private spaces.
The development forms a spacious landscaped setting, striking a balance between preserving privacy and providing visual openness towards the neighbourhood. The outdoor spaces play a key role in integrating the block into its urban surroundings and encourage shared use. Although reserved for residents, these walking areas remain visually open, offering a variety of green spaces conducive to multiple uses.
At the urban scale, the project creates a permeable landscape that establishes a direct link between the block and its surroundings. Tree-lined visual corridors extend the structural green network formed by the new roads, integrating the heart of the block into a sense of continuity with the public space and contributing to the clarity of the wider urban landscape.
At the block level, the central area is designed as an attractive and unifying space, extensively landscaped and equipped with furniture suited to multiple uses, both individual and communal. The communal gardens form the focal point of this layout. A genuine intergenerational meeting place, they are accessible from the adjacent streets to all residents of the four buildings.
The decision to raise the buildings by 0.80 metres helps to create a more intimate atmosphere for the ground-floor flats and enhances the block’s landscaped character. This layout also ensures continuity with the greenery of Rosa Parks Park and forms part of the ecological and urban network of the Bron-Terraillon ZAC.
New ways of living
This project grew out of a clear commitment: to design housing that is directly attuned to the habits and lifestyles of its residents, rather than prioritising an architectural statement in its own right. Above all, the aim is to provide an appropriate and adaptable response to the needs of a diverse range of people — students, families, and older people — by placing their daily routines at the heart of the design.
Beyond simply providing comfortable homes that comply with environmental requirements, the aim is to pioneer a genuine renewal of ways of living. This approach is reflected in a variety of housing types, ranging from one-bedroom flats to six-bedroom flats, enabling the project to cater for a wide range of residential situations and contributing to social and generational diversity at neighbourhood level.
This everyday architecture is reflected in a rich and varied range of options: a choice of floor areas within the same property type, single-storey or duplex flats, a variety of outdoor space layouts, private ground-floor terraces, as well as direct access from the outside. These choices encourage residents to make the flats their own and enhance the quality of living.
In line with this approach, duplex flats have been incorporated into the ground-floor level of two of the four buildings. Accessed via internal walkways within the plot, they offer residents a private entrance and help to create a more domestic connection to the communal space.
These family homes, situated on the ground and first floors, benefit from dual-aspect layouts and direct access from the centre of the block. They are thus akin to genuine townhouses, combining urban density with residential quality.
a highly efficient wood-concrete construction
The project is based on a construction principle that combines timber and concrete, aiming to make the best possible use of the intrinsic properties of each material in order to achieve overall performance, both structural and environmental.
The main structural system is based on a reinforced concrete framework. This choice ensures excellent long-term stability, enhanced resistance to mechanical stresses, and full compliance with regulatory requirements. The thermal inertia of the concrete also contributes to summer comfort by limiting overheating.
The project’s base, constructed from formwork concrete with a meticulous mineral finish, serves as a strong anchor within the site. It follows the topographical variations and ensures a seamless transition to the public space, contributing to the clarity of the ground floors and encouraging residents to appropriate them.
The loggias are designed as a permanent extension of the concrete structure, using a system of slabs and visible posts.
On the elevations, the non-load-bearing timber-frame façades complement this system by providing lightness and thermal performance. Prefabricated in the workshop, they allow for rapid and precise installation. Their design incorporates bio-based insulation and suitable cladding, helping to achieve the project’s environmental objectives, including RE2020 standards and the reduction of carbon emissions in construction.
The attics are constructed entirely from timber. This approach reduces the load on the underlying structure, optimises the foundations, and significantly reduces the project’s carbon footprint.
From an architectural perspective, it allows for a lighter design language, characterised by clean lines, setbacks, and generous terraces.
Bio-based solutions for environmental performance
Beyond this structural crossover, the project demonstrates a strong environmental commitment through the extensive use of bio-based materials, promoting carbon sequestration and reducing the overall environmental impact of the project.
Firstly, the timber-frame façades incorporate wood-fibre insulation combined with external thermal insulation, covered with a mineral render and installed in accordance with STO’s ATEX specifications to ensure durability and waterproofing.
At the back of the loggias, the timber-frame façades consist of wood-fibre insulation with vertical cladding made of autoclaved Douglas fir. Protected from the elements by the overhangs of the loggia slabs, this cladding retains its aesthetic appeal over time without uneven discolouration.
This approach extends to the interiors of the homes, particularly those for owner-occupation, with the installation of wooden flooring, which enhances comfort and quality of living.
All these choices enable the project to meet high standards, as evidenced by Level 3 of the Bâtiment Biosourcé label for owner-occupied homes and Level 2 for rental properties.
