Location: Tachikawa, Tokyo
Architects: Tezuka Architects
Engineers: Takenaka Corporation
Takaharu and Yui, the architects, designed an oval kindergarten with a roof that is a playground by itself. They worked hard to accommodate their design to the already existing nature of the construction site.
The structure of the building was a challenge for the designers. The roof has an oval shape; however, the geometry is not perfect so it does not have a center or a reference point for the structure. They came up with a triangular steel structure for the roof, which is much stronger than a two directional structure, as shown in the third image below.
Part of the roof structure can be observed in the image below. The roof was designed with openings for skylights and for the existing trees.
Numbers 1 and 2 represent these openings in the plan, respectively. All the openings can be accessed by the children from the roof. Beams marked with number 3 represent steel I-section main beams (300 mm deep). Beams labeled with number 4 are steel I-section longitudinal beams (260 mm deep), and beams with number 5 are steel I-section beams (140 mm deep). Main and secondary beams are shown in section in the image below.
The roof is made of 20 mm of cherry boarding, 60/45 mm battens, steel raising pieces, EPDM (rubber) layer, 50 mm layer of concrete, 50 mm layer of thermal insulation, 200 mm for mechanical services, other 50 mm of thermal insulation, 15 mm of plasterboard, and 9 mm of perforated plasterboard acoustic soffit. The roof is supported by tubular steel columns.
The kindergarten was designed with no walls between the classrooms. This way the children learn to develop their own concentration in open and loud places. There is just one permanent wall that was placed between the staff area and the classroom next to it. All the other walls are sliding walls made of triple glazing in wood frames.
The floor assembly is 14 mm of untreated pine parquet, 15 mm of plywood, 121 mm of an under floor cavity for warm-air heating, 40 mm of thermal insulation, 230 mm of reinforced concrete floor slab, a vapor barrier, a root-resistant sheeting, and a concrete leveling layer on 50 mm of gravel bed.
A special detail of the architecture of this kindergarten is the roof by itself. It serves as a playground and as a classroom for the children. The only other playground part besides the roof is a slide that goes from the roof to the ground. Around the edges of the roof there is a rail with vertical railings spaced at 11 cm of each other; this distance is too tight for the head of a child but big enough for their legs to pass easily. All 500 children of the kindergarten can sit on the edge of the roof to watch concerts or presentations.
Source: Kindergarten in Tokyo. Detail Magazine pgs 278-289 , 3rd Ed, 2008.