Clerestory Garden at Naka-Ikebukuro Park | Key Operation Inc/Architects

A mixed-use building integrating commercial facilities and residences, planned adjacent to Naka-Ikebukuro Park and located a two-minute walk from Ikebukuro Station East Exit. This project aimed to harmonise with the mixed-use cultural and commercial facility ‘Hareza Ikebukuro’, which opened in 2019, and the renovated Naka-Ikebukuro Park, seeking to create new appeal for the area. Naka-Ikebukuro Park underwent a transformation during its renewal, shifting from a sandy surface to a stone-paved plaza. Re-established as a space evoking the character of a European square, it now functions as a venue supporting cultural events and vibrant activity. Creating a sense of unity with this plaza became a key theme in the building's façade design.

Given the site's frontage onto the plaza, the project leveraged the relatively relaxed height restrictions. By setting floor-to-ceiling heights at approximately 4 metres, an internal space conveying a sense of expansiveness was achieved despite the limited plot area. Furthermore, to complement the plaza's lush green environment, the building's exterior incorporates extensive planting. Although wall greening was considered, in order to ensure visibility within the tenant spaces, a “transom garden” was created by installing three-dimensional planting in the 2.2-metre-high windows (the maximum height for aluminium sash fire protection equipment) and the transom sections above them. This three-dimensional garden gives the building a green impression that is more in keeping with the square, in contrast to the hard impression of the surrounding buildings. While the transom gardens are set back into recesses, the lower part of the building extends to the edge of the site, creating an efficient cross-sectional shape that maximises the leasable area for tenants. This garden area is not merely an exterior design feature; it has been designed to be enjoyed from inside the building as well, functioning as an attractive space particularly on the lower floors, where cafés and similar uses are envisaged, and on the upper floors, where residences are located.

The front of the building prioritises the main first-floor tenant, so the stairs and lift are accessed from the side road. The tenant spaces on the first and second floors can be used independently, but the design also allows for integrated use with the installation of internal stairs and a dumbwaiter. Tenants such as shops and clinics are envisaged for the third to sixth floors, while the seventh and eighth floors are maisonette residences. The residential sections feature living-dining areas and kitchens. The inclusion of lofts transforms these two-storey maisonettes into four-storey “Quartets”, creating a densely layered cross-section. The eighth-floor living space incorporates a curved atrium. A net suspended within creates a hammock-like environment, complemented by a bouldering wall allowing access to the upper levels. The seventh floor houses private rooms and wet areas, realising a three-dimensional living space that utilises circulation routes incorporating elements like a slide. 

Initially, the plan was to establish a structural frame matching the polygonal exterior shape following the site's form. However, considering cost efficiency, a simple grid form was adopted for the structural frame in the central section. This allowed the building's exterior to follow the site's shape while enabling efficient structural design internally. At the rear of the transom garden, windows aligned with this grid frame were installed. This creates the “Luce Jardin” (Light Transom Garden), where natural light softly filters through the transom's plantings into the interior. Furthermore, timber was used on the underside of the transom garden's eaves. Unlike the façade visible from the elevation, this creates a second façade visible when looking up from eye level, lending warmth to the entire building.

This project proposes a new form of public architecture for a mid-rise building in the city centre. It maximises the floor area ratio while creating porous volumes with interstitial spaces for planting. This fosters a sense of unity with the plaza, harmonises with the urban landscape, and provides a rich environment.

Credit information

Architecture : KEY OPERATION INC. / ARCHITECTS

Photography : ToLoLo studio Mayu Nakamura


Project outline

Project name : Clerestory Garden at Naka-Ikebukuro Park

Location : Toshima-ku, Tokyo

Completion : 2025. 01

Principal use : Shop + Residence

Structure : Steel-frame construction

Site area : 82.84 m2

Building area : 65.47 m2

Total floor area : 469.06 m2

Contructor : Watanabe Construction Co., Ltd.

Structural engineer : Delta Structural Consultants

Facilities: Comodo Facilities Planning

Architects: KEY OPERATION INC. / ARCHITECTS