NIKKEN SEKKEI revitalizes 'triangle building' with vivid public space topped by glass roof

reviving the urban business district

NIKKEN SEKKEI brings new life to ‘shinjuku sumitomo building’ or the so-called ‘triangle building’ constructed in 1974, creating a vivid public space topped by a huge glass roof. along with the expansive atrium roof ‘sankaku hiroba’ (triangular plaza), proper renovations at the center tower took place. located in tokyo’s business district, this project broadens the opportunities to enliven and improve the value of such large-scale structures by using maintenance practices.

taking shape as an accessible gathering place, the project utilizes innovation and new technologies, tackling numerous challenges. since the early 2000s, the nishi shinjuku area, already serving as a business district, faced the challenge of how to reanimate an increasingly diverse city. as a result, local public and private sectors joined hands to create a more lively and appealing city, meeting the demands of a new era.
all images courtesy of SS unless stated otherwise

renovating a high-rise building while in use

the renovation project by NIKKEN SEKKEI (see more here) was undertaken while the building remained in use. located in the privately-owned area of the building’s outdoor plaza, the construction of the massive glass roof was performed concurrently with major repair work. the huge steel-structured roof (L:140m, W:90m, H:25m) covers a central space devoid of columns. expansion joints were used above ground so the roof could be structurally independent. roof-supporting columns were strategically concentrated along the site’s perimeter and the existing periphery in order to minimize the effects on facility renewal and other activities.

simultaneous with the construction of the roof, seismic retrofitting was performed on the entire building to better counter earthquake-related effects and vibration. using the building’s existing equipment balconies, second-floor inertial rotary damping tubes were installed to connect up to the 49th floor in order to absorb the building’s kinetic energy. all of the tasks were performed without disturbing the building’s exterior or office workspaces.

inheriting the landscape and redesigning the legacy

the shinjuku sumitomo building is called ‘sankaku (triangle) building,’ both for its distinctive appearance and for its impressive interior and exterior detail. the architects sought to redesign spaces that respect the legacy landscape: red granite formerly used in the exterior (now no longer mined) was reused in the walls of the vehicle entrance; and bricks from the former outer wall design (inspired by the yodobashi purification plant’s brick motif) were ‘recreated’ using laminated bricks that integrate air conditioning, sound deadening, and wall greenery functions. 

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project info:

name: shinjuku sumitomo building
designer: NIKKEN SEKKEI

basic plan general supervision: sumitomo realty & development co., ltd.

construction drawings and supervision: taisei design planners architects & engineers

location: shinjuku-ku, tokyo japan principal

total floor area: 180,195sqm, including atrium (6,700sqm)

floors: 4 basements, 54 above ground (3 mezzanine)

maximum height: 211.35m

year: 2020 construction: taisei corporation

photography: SS; harunori noda (gankohsha)

designboom has received this project from our ‘DIY submissions‘ feature, where we welcome our readers to submit their own work for publication. see more project submissions from our readers here.

edited by: christina petridou | designboom