Atelier du Ralliement

Toue Cabanée . Le Cellier

Atelier du Ralliement + Clémence Mansons . Collectif Saga . photos: © François Massin Castan

Nestled in a rural enclave near Nantes, this small single-family home is uniquely positioned between two distinct environments: a parking area linked to a train station on one side and a remarkable natural landscape featuring a cliff, moss, and trees on the other. In its original state the small single-story structure, reminiscent of a gardener’s hut, required expansion to accommodate a modern family’s everyday needs. With its initial footprint of just 28 square meters, the project sparked an intriguing exploration into designing a functional and lively home within the existing space, without expanding the ground area.

The radical vertical addition offers the opportunity to avoid views of the parking lot and instead incorporate multiple, impactful elements of the natural environment into the home. The ecological and sustainable design strategy considers various orientations to capture different natural light throughout the day and numerous options for natural ventilation.

On the ground floor, carefully designed openings, both repurposed and newly created, offer direct views of the cliff and its unique vegetation, primarily ferns and moss. The intermediate level features living spaces that fully open onto the opposite facades, creating intimate and sensitive connections with the surrounding nature. Sliding windows span the full width of the walls, allowing for natural over-ventilation when needed.

The upper story conforms to the shape of the asymmetric roof and accommodates two bedrooms, separated by a spacious void that extends beyond the stairwell. Continuous roof windows flood the area with natural light and create an inviting observatory for sky gazing.

A vertical core connects these three levels, integrating multiple functionalities into a unified design element. Beyond serving as a staircase, it addresses structural bracing needs, strategically positioned at the center of the house due to expansive openings in the intermediate level’s side walls. Utilizing this core as a staircase creates a distinctive «K-shape,» with design nuances that vary depending on the level. On the ground floor, the base of this structure incorporates storage solutions, including discrete compartments for appliances such as the fridge, and others hidden behind removable wooden block stairs. As it ascends to the living room, the core becomes lighter and more transparent, facilitating a strong visual connection between both sides of the space. This vertical configuration enhances climate control throughout the seasons, particularly in summer. The ground floor, nestled in an enclosed setting, remains naturally cool, while numerous roof windows on the upper levels allow for effective heat extraction in the evenings.

Through the design and prefabrication of a significant portion of timber components for the new walls and roof frameworks off-site, the on-site intervention for the structural part was completed in just one day, swiftly bringing the new volume to life. This approach significantly shortened the construction period to a mere 4 months from initial preparation to achieving airtight, waterproof volumes. Applied to existing buildings, this prefabricated method could be replicated in similar scenarios to reduce construction timelines and promote densification.

The ground floor, the sole existing structure prior to expansion, incorporates external wooden wool insulation. This material was also utilized in the new walls, promoting a diverse selection of wood species, including chestnut for the new floors, an exposed spruce structure, pine plywood for the inner walls, and wicker reeds on the entire facade. Combined with a staggered envelope design, these materials collaborate to create a smooth and delicate architecture that resonates with the surrounding landscapes.
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• ©AdR Atelier du Ralliement + Clémence Mansons
• ©FMC François Massin Castan
• ©Saga Collectif Saga (co-designer/builder of the central inner staircase)

Original Building Year : 1952
Construction Year : 2021-2023
Program : Individual Housing
Type : Transformation of an existing single-storey house into a three-storey vertical house on the same footprint.
Original Sqm : 28 sqm ; Addition Sqm : 44 sqm ; Total : 72 sqm Plot Size : 251 sqm

Maîtrise d’ouvrage : Privée | Maîtrise d’oeuvre : Atelier du Ralliement / François Massin Castan, avec Clémence Mansons architecte hmonp | BET : VSB Vivier Structures Bois | Année : 2021-2023 | Mission : complète | Surface SP : 28m2 (existants) + 48m2 (créés) | Coût travaux : 170k€ ht | Caractéristiques environnementales : Structure épicéa, Menuiseries mixtes bois/alu, Isolation laine de bois (principale) et laine de chanvre (complément), doublage pin des landes, sol châtaignier, poêle bois, aucune emprise au sol créée