© Noriyuki Yano
The façade features a golden skin to create a striking sense of luxury. Backlit flexible plastic signage panels are installed vertically in front of the staircase façade.
感谢 KEY OPERATION INC. / ARCHITECTS 对gooood的分享
It is a compact building for rent, located at the intersection of Hanasaki-dori Street and Ginza Pedestrian Street.
▲建筑概览©Noriyuki Yano
Tokyo's famous Ginza business district is home to some of the highest prices in Japan. Although the site is only 6.27 meters wide and 5.46 meters deep, such a high price requires a detailed evaluation of the option to boost rental income. If only three floors are designed, there is no need for an elevator, but this makes the number of rental rooms smaller. If there are more floors, an elevator will have to be installed. If stairs and elevators were installed along the depth of the site and each floor was rented separately, a common corridor would be required, leaving little leasable space on the ground floor. If stairs and elevators are installed along the width of the street façade, the common corridor can be omitted, but the view of the street from the interior will be obscured, and the balconies necessary for escape cannot be installed on the third floor and above. The final plan for the building is a master lease of the building, which will consist of five floors of above-ground space and one basement. Staircases and elevators are arranged along the depth of the site, targeting tenants such as high-end restaurants, jewellery stores or watch stores.
▲夜景©Noriyuki Yano
▲建筑特写©Noriyuki Yano
In order to install stairs and elevators on one side of the building, the foundation walls needed to be kept only 200 mm away from the site boundary. This makes it impossible to use conventional retaining wall construction methods. In the end, the "open caisson construction method" was adopted in the following way: a precast concrete foundation on the ground was used as an open caisson. The basement is then excavated and cleared so that the caisson can sink below ground under its own weight. General contractor Ohara Komusho had experience with this approach in the past and therefore provided the project with expertise that would normally only be used in civil engineering.
▲楼梯 ©Nariukki Yano
▲天窗©Noriyuki Yano
The foundation is 6 meters deep into the ground, and the rest is located directly on the load-bearing layer. The first open caisson was poured 2.5 meters deep. In order to better allow the caisson to settle under its own weight, a tapered metal base was installed for it, which made the front edge sharper. The earthwork excavated at the front edge enters an open caisson that serves as a retaining wall on all sides, from below. Once the 2.5-meter caisson has been lowered to a sufficient depth, a 3.5-meter caisson is poured over it, and the foundation can be sunk even deeper. Adjusting the horizontal position of the caisson during the sinking process and at the same time making the caisson sink smoothly is a very difficult job. In the process of locating the foundation, it is possible that the soil at the foundation was suddenly eroded due to the flow of groundwater, causing the sinking of an adjacent 70-year-old three-story timber structure without foundation. Although it took additional time to dismantle the adjacent building and adjust the caissons, the underground works were completed after the pouring of the underlayment and the plinth beams.
▲Noriyuki ©Yano
▲入口©Noriyuki Yano
▲设备间©Noriyuki Yano
Due to the small footprint, the steel structure on the ground needs to be as slim as possible. We used 150 mm and 125 mm square thick-walled steel columns called "Kaku Hotto". The first and second floors are covered with a fire-retardant coating called "Cera-tighca" to meet the 2-hour fire resistance specification, and the 3rd floor and above are covered with a fire-resistant coating with a 1-hour fire resistance rating.
▲Noriyuki ©Yano
▲精致的布局©Noriyuki Yano
In the basement there are storage rooms and utility rooms, in which inlet and distribution boxes, telecommunication cabinets and drainage pipes are installed. On the ground, there is a small space of about 50 cm on the west side of the site for the installation of water meters. Since it was difficult to secure space in the cistern, the architects made a recess under the front window frame to provide space and facilitate access. The staircase is installed at the front of the building, allowing for quick access to the exit in the event of an emergency evacuation.
▲立面细部©Noriyuki Yano
On the west side of the building, there is an outdoor conduit space for vertical movement of service facilities and the installation of air intakes. In order for tenants to be able to decorate individually in the future, panels were installed in the duct space of each floor's façade for easy access. The pipe space is protected by a metal mesh.
▲检修面板 ©Naryukki Yano
▲检修面板 ©Naryukki Yano
The façade features a golden skin to create a striking sense of luxury. Backlit flexible plastic signage panels are installed vertically in front of the staircase façade. While the roof balcony was primarily used for the outdoor units and exhaust units of the air conditioner, the architects added a bar counter for meals and windows overlooking the street and surrounding buildings.
▲屋顶 ©Nariukki Yano
▲屋顶景色©Noriyuki Yano
Project drawings
▲平面图©KEY OPERATION INC. / ARCHITECTS
▲剖面图©KEY OPERATION INC. / ARCHITECTS
▲结构分析©KEY OPERATION INC. / ARCHITECTS
Use：Tenant Building
Stories：5F+B1F
Structure：Steel frame
Site area：34.28 m2
Gross Floor Area：28.34 m2
Total Floor Area：167.76 m2
Location：Chuo ward, Tokyo
Completion：2022.03
Planning：Landpool Co., Ltd.
Design：Akira Koyama＋KEY OPERATION INC. / ARCHITECTS
Structural Engineer：Delta Structural Consultants
Building Equipment：Comodo
Contractor：O’hara Architectural and Construction, Ltd.
Photography:Nariuki Yano