The Shinjuku Sumitomo building, fondly known as Sankaku (triangle) Building, is a high-rise building located in Tokyo. It was designed by Nikken Sekkei, and construction was completed in 1974. The building is known as a centre of tourist attraction due to the most recent renovation that involved a huge public space covered by a glass roof. The building is 52 stories tall, with a height of 211.4 metres. The building location is at the heart of the city, and it had to adapt its surrounding elements.

Shinjuku Sumitomo building by Nikken Sekkei - Sheet1
Approach view of Shinjuku Sumitomo building_©Kentaro Nemoto.

On approach, the Shinjuku Sumitomo building looks like an ordinary high-rise office building, but first looks can be deceiving. A closer inspection is all it takes to show the true nature of the design approach, construction method, and techniques used in this building.

Philosophically speaking, Nikken Sekkei adopted a minimalist approach to this building design. He deemed it fit to avoid using any unnecessary element, focusing on only what is required to create a simple form that fulfilled the desired function. Here, he believed that less is more.

The design concept stemmed from the philosophy that less is more and less is required to create a high-rise structure that would blend seamlessly with the surrounding urban landscape while also providing a sense of openness and lightness.

The building planning required careful consideration of the building form, site location (a bustling commercial district), urban scape, building orientation, culture, natural lighting, and the effects of natural disasters, especially earthquakes. The building was designed with a flexible and modular structure, allowing it to adapt to the changing needs of its occupants over time. The building form was optimised to reduce the energy needed to control the thermal comfort within the interior spaces. The towering part of the building form is symmetrical, while the lower floors have asymmetrical shapes and curved lines, giving it a unique and modern appearance. The design involved a floor plan with a triangular shape and chamfered vertices. The building floors were designed with lightweight concrete to reduce the overall weight.

Shinjuku Sumitomo building by Nikken Sekkei - Sheet2
Arial view of Shinjuku Sumitomo building_©SS.

When looking at the design style, we find sleek, clean, and uncluttered aesthetics. A symbol of class and modernism. The building’s exterior features a series of straight and curved lines that flow seamlessly from one level to the next, creating a sense of movement and dynamism. This helps in wind resistance, increasing the building’s energy efficiency. Using transparent material such as glass creates a feeling of transparency and openness, allowing natural light to flood into the building’s interior spaces.

The choice of building materials was a combination of traditional and modern materials. There is timber, concrete, steel, and glass, a feature notable in contemporary architecture. Also, the use of concrete in the lower levels of the building provided a sense of a stable structure and durability to withstand the building location’s prevailing conditions.

The design approach to sustainability is seen in the choice of building materials. The building is designed with energy efficiency at heart to reduce its carbon footprint. The building’s simple, open floor plan allows for various uses and adaptability to changing needs over time. This is particularly important in a city like Tokyo, where real estate is at a premium and buildings need to adapt to changing needs.

Shinjuku Sumitomo building by Nikken Sekkei - Sheet3
Interior of Shinjuku Sumitomo building_©Harunori Moda (Gankohsha).

The construction of the Shinjuku Sumitomo building began in 1971 and lasted until 1974. Having a complex roofing system at the lower level, the construction required the latest, cutting-edge technology of the time. Steel members and modular parts of the building were pre-fabricated offsite and assembled on-site. This also helped reduce the construction process’s duration, with minimal disruption to the surrounding area. The structure was constructed to meet the earthquake’s resistant standards, using advanced structural systems and materials to ensure stability and safety.

In terms of innovation and inspirational elements, Nikken Sekkei used steel panels with a double-skin facade for the walling. This double-skin facade consists of two layers of glass. The first layer of glass serves as a sun shade, reducing the amount of heat penetrating into the building and the solar glare. The second layer, on the interior side, is perforated with small holes, allowing for natural ventilation and providing a sense of connection to the outside world for the building’s occupants.

Shinjuku Sumitomo building by Nikken Sekkei - Sheet4
Interior showing the atrium roof of the Shinjuku Sumitomo building_©Harunori Moda (Gankohsha).

For a building this size, the regular renovation approach will be to shut down the whole building or at least the part that has been renovated. The Shinjuku Sumitomo building was in full operation during its renovation, which was completed in 2020. The contractors could not disrupt the bustling business district for a renovation. However, as far as safety measures go, it took a lot of work to ensure them.

The renovation works consisted of installing a huge glass atrium roof over a public space and other major repair works within the building. 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 minimise the effects on facility renewal and other activities. 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.

Plan views of the Shinjuku Sumitomo building_©

.[/caption]In conclusion, Nikken Sekkei showcases the power of an austere design. With a simple, uncluttered appearance, sustainability, and functionality at heart, timeless-modern architecture was achieved.


Archidaily- Hana Abdel (2022). Shinjuku Sumitomo Building / Nikken Sekkei + TAISEI DESIGN Planners Architects & Engineers. [online]. Available at: [Accessed 15 December 2022].

Design boom (2022). NIKKEN SEKKEI revitalizes ‘triangle building’ with vivid public space topped by glass roof. [online]. Available at: [Accessed 15 December 2022].

Inax (2022). Shinjuku Sumitomo Building. [online]. Available at: [Accessed 15 December 2022].

Skyscraper center (2022). Shinjuku Sumitomo Building. [online]. Available at: [Accessed 15 December 2022].


Ebelechukwu Ubaka is an Architect and a Writer with a zest for creating healthier and happier lives through Architecture solutions. She shares her views and opinions about Architecture and Architectural practice in Nigeria. She is on a mission to educate clients about how architects play a major role in their lives and how they can take advantage of such services.