Yotsuya Tenera, Key Operation Inc. / Architects, Tokyo, Japan.

Yotsuya Tenera: a great example of how the limitations of a site provoke the most interesting architectural moments. A small site in the dense, historic area of Tokyo — Shinjuku — offered Key Operation Inc. few obvious ways of orienting twelve apartment units in accordance with strict setback rules.

After the jump, video and much more information.

Key Operation Inc. / Architects found a solution in two of what they call “tree-shaped void spaces,” meaning two compact, open-air staircases that service each apartment and abut each balcony.

By pushing the unit volumes to the back of the site, they were able to satisfy evacuation requirements and the access issues with a 2m-wide ground-floor entrance hallway. The two staircases rise from the ground floor, and the layout of the unis depend entirely on the staircase. The result is a series of discreet floorplans that maximize sell-able floor area by reacting only to the single continuous void space that runs up to the roof.

From the architects:

Site & Code Regulations

The project site is in a five-minute walk from Yotsuya Station located in a quiet residential area right behind the Shinjuku Street. This area holds many temples, shrines and also fairly dense housing. Like a spreading network of space, those houses and complexes fill the blank spaces between the streets and alleys. This housing complex was planned to be built on the site of a crank space with 10m of the frontage and 17m in depth. Due to the regulation for Shinjuku Ward studio apartments, 12 units of the housing complex was planned out including 9 units of less than 30m² of the floor area and 3 units of more than 30 m².

Volume Layout and Flow Lines to Maximize the Rental Area

The project site has 2m of setback from the property line. Normally the set back is tending to be provided to the south, and an approach is set to the north in order to gain the day light. However, the neighboring land located on the south of the project site has a passage to their flag-pole-like plot. And because of this condition on the south, adequate amount of daylight was expected to flow towards the project site. In order to gain as much of the building area as possible, the building mass is pushed towards the south, and the setback space is utilized as an approach garden and it also works as the evacuation passage which needs to be more than 2m width. As a result of the overall layout, the circulation space was studied in order to make all the 12 units accessible contained in the L-shaped volume. In this scheme, 2 void spaces were provided within the building mass as functioning stairways. With this compact stair cases, the floor areas of the rental area is increased. By using an efficient approach, the area of the common space was reduced even more efficiently than the typical one-sided corridor scheme.

Continuous Tree-Shaped Void Space into the Gaps in Yotsuya

In general, this kind of internal staircase tends to be claustrophobic space. However, the void space is linked with each residential unit’s balconies as continuous Tree-Shaped Void Space and spread throughout the balconies, towards the gaps in neighboring residential buildings, the courtyard, the passage at the back, and the neighboring apartment corridors. Considering the ventilation purpose for the balcony areas, the vertical steel bars separating the staircase from the balconies carry the vertical load of the stairs and lighten up the spaces with the open structure. Also, the skylights bring the natural day light and help promote the chimney effect to ventilate the spaces.

Diversity of Dwelling Units

Every dwelling unit has been formed to surround the Tree-Shaped void space. Depending on the exterior walls and the shapes of the void, all units have different floor layouts: L-shape; I-shape; T-shape; and C-shape. The simple shape of 20 m² units is provided for a single person, and a couple or two people would occupy 30 m² units in the other shapes. For example the C-shape unit provides the distance and the cut the vista in order to create the privacy between the two occupants of the unit. All the dwelling units have either balcony spaces or terraces. Walking into a dwelling unit from the staircase, through the dwelling unit, and come out to the balcony. the staircase appear once again. The far end of each unit is linked with the entrance area at front through the void. Keeping the great sense of privacy in the unit layout, this void is meant to create a sense of community and encourages interactions among dwellers.

Texture on the Concrete Wall

Concrete texture of this project is one of the important design criteria. In comparison with the surrounding buildings, the volume of this complex is relatively larger, but it still balances up with the scale of the surrounding buildings with its appearance; harsh cast concrete finish was softened with wood texture to create friendly and harmonious appearance. In general, cedar plywood is used for formwork. However, the construction cost needed to be cut in the process. Therefore, larch plywood was chosen for the formwork. Knowing the facts that larch wood would absorb a lot of moisture and be bent up and that its grain wouldn’t come out well on the concrete surface, varieties of plywood were also tested initially in the process. By experimenting different wood materials in the process of formwork at the base, larch plywood was coated with damp proof material, and remover was painted on the surface before casting concrete. At the end, the grain came out beautifully on the surface of the concrete. The galvanized metal frames were attached to the openings. The metal frames give an accent to the wood-textured concrete stand out and prevent the windows from rain water to smudge the facade. Moreover this frame can cut the view from one unit to another at the L-shape volume of this building. The balcony space interlocked with the staircase connected to the open space towards the surrounding neighborhood and also visually linked with the court yard as if they were to represent the neighboring streets of this intricate area. Setback space is not provided only for a buffer space to cope with the regulation, but also functioning as an attractive courtyard space to provide great views to each dwelling unit. As a result, the whole complex has become blended into Yotsuya with lots of green and many alleys

For more on Yotsuya Tenera, visit its Architizer Project Page, or check out the profile of Key Operation Inc. / Architects.

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