Soft concrete may be an oxymoron, but Ellipse Sky, a four-story residential building designed for an obstetrician, his family, and several tenants, deftly pokes holes in that notion. A concrete box on the western edge of Tokyo, the house is the first freestanding structure by Keiko + Manabu, a young design duo specializing in commercial interiors. The pair teamed with engineer Akira Suzuki to craft a building that mollifies the hard material with swooping arches, graceful details, and walls as smooth as a baby's bottom.

The decision to build with concrete was a given from the start when the client purchased a plot near his birthing center and invited three firms'all with female principals'to participate in a design competition. Approaching the brief with the vision and sensitivity of interior designers, partners Keiko Uchiyama and Manabu Sawase presented a large-scale (1:20), easy-to-understand model and landed the commission. 'This is a very important scale for us,' says Uchiyama. 'It is where you can imagine the inside from the outside.'

Connected by an exterior concrete stair and elevator, the building consists of a duplex apartment on the top two floors for the doctor, his wife, and their two children (both medical students), independent quarters for his mother on the second floor, and six duplex rental units accessed directly from a garden walk at grade. But the project took three years to complete, partly because of the laborious construction process needed for the concrete's carefully conceived forms.

Wanting to offset the rigidity of the cubic building, the design team devised a facade punctuated by a series of apertures: large ones that maximize unimpeded sky views from within, and small ones that edit out the neighborhood dominated by small-scale apartment buildings and single-family homes. A tall, narrow arch framing the elegant spiral stair marks the entrance to the family quarters. 'We wanted many openings, so the wall had to be as thin as possible,' notes Uchiyama. Affixed to the building for stability, but essentially self-supporting, the facade measures a mere 9 inches thick at the edge of the arches.

Because of their shape, the wall's convex curves could not be completed with straightforward pours, requiring vibration to coax the concrete under inverted crowns. Yet this was child's play compared with the complex 3-D formwork used for the curvaceous stair, with its subtle oval plan and concave undersides, and the varying ceiling heights at every level.

This dynamic element spirals up to the doctor's home, a 2,960-square-foot duplex entered on the third floor. Here an L-shaped terrace mitigates the site's irregular geometry, while shielding the interior from direct sunlight with a cantilevered roof 20 feet above. Inside, a foyer leads to a reception room and the family's open living/dining room and kitchen, framed by full-height, arched windows facing the terrace. A bathroom, workroom, and master bedroom are tucked behind these public areas. Internal stairs connect to the children's rooms and a second bath above. Compact by comparison, each 431-square-foot rental unit features a multipurpose space on the ground level and sleeping quarters above'perfect for a couple with a baby.

Uchiyama and Sawase carefully considered wall surfaces and details. 'In the United States, fun finishes are common, but because Japanese houses are smaller and people rarely entertain at home, they get less attention,' Uchiyama explains. They used patterned wallpaper and decorative paint to add homey touches to the rentals, and drew from their usual palette of commercial materials'tile, terrazzo, and slatted window blinds'to complement the concrete surfaces within the doctor's home.

In the end, the concrete itself showcases the designers' talents most effectively. Treating the interior with the same finesse as the building's large architectural gestures, they created velvety concrete walls by coating the formwork with urethane. Then they softened harsh, rectilinear wall openings and corners by refining them with playful cutouts.

Thanks to exacting design standards and highly skilled contractors, legions of Japanese architects have been achieving remarkable results with concrete since before Uchiyama and Sawase were born. But few have fundamentally changed its character and expression. By placing as much value on the detailing inside Ellipse Sky as on the wow factor of the building's external form, Keiko + Manabu has mastered the tough material's tender side.

Completion Date: August 2012

Size: 7,677 square feet

Cost: withheld


Owner: China Central Television

Office for Metropolitan Architecture (OMA)
Heer Bokelweg 149
3032 AD Rotterdam
T: +31 10 243 82 00
F: +31 10 243 82 02

Personnel in architect's firm who should receive special credit:
The CCTV project was led by OMA / Rem Koolhaas, former OMA partner Ole Scheeren (until 2010), partner David Gianotten and project manager Dongmei Yao in close collaboration with partners Shohei Shigematsu, Ellen van Loon and Victor van der Chijs.

The design team consisted of project architects Anu Leinonen, Charles Berman and Adrianne Fisher together with Design team(A-Z): Alain Fouraux, Arianna Spaccasassi, Antonio Teles Branco, Beatrice Schiavina,  Beatriz Ramo Lopez, Catarina Canas, Charles Gosrisirikul, Chris James, Christina Murphy, Chris van Duijn, Daan Ooievaar, Dan Cheong, Dirk Zschunke, Dorthee Dietz, Erez Ella, Fang Tieying, Faustina Tsai, Feng Pei, Fernando Donis; Florian Pucher, Gabriela Bojalil, Gaspard Estourgie, Georg Bucher, Gonzalo Laurentiu Coceanga, Hendrik Gruss, Guillaume Colboc, Hiromasa Shirai, Holly Chacon,  James Harper, Jasmine Tsoi, Jeffrey Bolhuis, Joao Bravo Da Costa, Joao Gomes Branco Teodosio, Johannes Buchholz,  Joris Fach, Joseph Monteleone, Keren Engelman, Kam Fai Tai, Laurent Troost,  Lawrence Leung, Li Guilin, Liu Xiaodong, Lodewijk van Eeghen, Loy Tsao, Mamen Escorihueles, L. E. Tsao, Manuel Shvartzberg, Max Burianek, Max Rink, Max Schwitalla, Melissa Dowler, Menno van der Meer, Michel van der Kar, Paul Burgstaller , Paul Kroese,  Pedro Costa Gama, Peter Lee ,Roberto Otero, Rodrigo Nunez Carrasco, Rodney Eggleston, Sarah Gibson, Shi Wenchian, Shiro Ogata, Steffen Ell, Steffie Wedde, Steven Smith, Stuard Maddox,  Suse Koch, Tammo Prinz, Ted Lin, Tim Callaghan, Torsten Schroeder, Victoria Willocks, Wang Xinyuan, Wang Yunzhu, Wu You, Xu Tian Tian, Yimin Zhu, Yiannis Kanakakis, Yu Long, Zhaohui Wu; and Support team (A-Z): Lisa Aalders, May Yan Fan, Li Dan, Liu Aoshuang, Liu Yonghong, Sun Yongzhen, Ou Qiang, Wang Yimeng, Wang Yu, Wu Xinghua, Xu Yi, Zhang Yajuan, Zhao Xiaoyue

Architect of record : OMA/ECADI

Interior designer: OMA/ECADI

Engineer(s): ARUP/ECADI—Cecil Balmond, Chris Carroll, Michael Kwok, Rory McGowan, Paul Cross, Xiaonian Duan, Craig Gibbons, Goman Ho, Richard Lawson, Alexis Lee, Andrew Luong, Chas Pope, design team

Local design institute:
East China Architectural Design & Research Institute Co. Ltd.  (ECADI)
No.151 Hankou Rd. Shanghai, 200002
Tel: 0086-21-63217420

Structure, Services, Fire, Security Engineering: Arup, London/Hong Kong/Beijing 
Facade Engineering and Design Consultancy: Front Inc, New York
Lighting: Lighting Planners Associates, Tokyo
Acoustical: DHV Building and Industry, Eindhoven
Landscape: Inside/Outside, Amsterdam

Broadcast Consultancy: Sandy Brown Associates LLP, London
Theatre Consultancy: Ducks Scéno, France 
Vertical Transportation Consultants: Lerch, Bates & Associates, London
High Rise Consultant: DMJMH+N, Los Angeles 
Foodservice Consulting and Planning: Romano Gatland, New York
Signage / Graphics: 2x4 Inc, NY
Strategic Advisor: Qingyun Ma, Shanghai

General contractor: China State Construction Engineering Corporation

Iwan Baan, Jim Gourley, Phillippe Ruault

Crystal CG

CAD system, project management, or other software used:
AutoCAD, 3Dmax, Rhinoceros, SketchUp, Very, Microsoft office, Adobe design



Structural system
Steel Fabricator:
Address: Baosteel Tower, Pu Dian Road 370, Pudong New District, Shanghai, 200122, P.R.C
Telephone:86 21 58350000 / 58358888
FAX:86 21 68404832
Sales Hotline:400-820-8590

Jiang Su Huning Steel Mechanism CO. Ltd.
Address: 605-1, Building No. 76, East 4th ring road, Chaoyang District, Beijing, 100124, P.R.C
Telephone: 010-59626325 010-59626137 010-59626136
FAX: 010-59626325
Sales Hotline:400-820-8590
Email: ,

Exterior cladding at plinth: BROWN TRAVERTINE

MANUFACTURER:Yingliang Stone Co., Ltd.
Address: R-12# Baoshui Market Building Xiangyu Road Huli Area Xiamen China
Telephone: 0086-592-6024097

Metal/glass curtain wall system: Beijing Jangho Curtain Wall CO., LTD
Jangho Beijing (Headquarters)
Address:No. 5, Niuhui North 5th Street, Shunyi District, Beijing 101300
Toll Free: 400-650-1166
Tel: (86)010-60411166
Fax: (86)010-60411666/555/888

Manufacturer:CSG HOLD CO, LTD
CSG Headquarters
Address: CSG Building, No. 1, 6th Industrial Road, Shekou, Shenzhen, P.R.C. 518067
Telephone: 0755-26860666
FAX: 0755-26692755

Stone paving and stone laminated Ceiling in lobbies: Yellow travertine
Manufacturer: Yingliang Stone Co., Ltd.
Address: R-12# Baoshui Market Building Xiangyu Road Huli Area Xiamen China
Telephone: 0086-592-6024097

Stone laminated ceiling fabricator:
Beijing Ispert lamination material corporation
Address: 6 Street, Guoxing, Guoxian Industrial Development Zone, Tongzhou District, Beijing
Telephone: 010-80587099, 13901360204/13301226280

Tower 1 core cladding: Corten: 3mm thick corten
Material provider: Shanghai Gate Construction Consulting Co. Ltd
Address:RM1503£¬No.1 MingHua Building£¬No.525 FangXie Road
Post: 200011

Lighting (major brand used)

Address: 811 Jiang Chuan Road, Minhang, Shanghai, China (Mainland)
Fax: 86-21-24083488