A space for learning under a leaf-shaped roof

Karuizawa is a quiet resort area located in the geographical center of Japan. This wooden, single-story licensed nursery school in the south of the town area was designed amid a natural setting.

Sited near Lake Shiozawa and Kazakoshi Park with a view of Mount Asama, the location provides a scenic and inspiring learning environment. Utilizing the green slope of the elevated neighboring land on the south side of the site, the playground is located on the sunny southern side. The leaf-shaped building is positioned diagonally at the center of the site, naturally dividing the south-facing playground from the north-facing parking lot. On the west side, where an existing retaining wall already existed, fences and other barriers were minimized to create a safe and harmonious layout that blends seamlessly with the surrounding environment.

A “free” childcare space for kids

Uniquely, the building has two roofs of different heights. This design includes a leaf-shaped floor plan that allows all childcare rooms to face the larger garden. The lower roof houses the childcare rooms, while the higher roof accommodates the hall and staff areas. The hall, located under the higher roof, serves as the center of the facility. It is spacious and tall enough to accommodate all the children, providing a space for free and creative activities. Large windows brighten the space and allow children to experience the changing seasons and the rich natural surroundings of Karuizawa.

On the east side of the hall is the staff room, which features a large white wall where the children’s creative works are displayed. On the west side of the hall is the kitchen, designed with glass walls so that children can observe the cooking process. These features create an environment where children are constantly exposed to various learning opportunities.

On the other hand, each nursery room under the low roof has a lower ceiling compared to the hall and is designed on a smaller scale suited to kids. As the children spend most of their day in the nursery rooms, they have been designed so that they can settle into them as their own spaces.

The six nursery rooms are divided into two zones, according to age: 0-2 and 3-5 years old. Each space is connected to the hall by wooden columns, making for a gentle space transition.

By creating one large space throughout the entire facility, children can move around freely, promoting interaction between different age groups and encouraging interest in the hall activities.

The children's spaces are also finished with wood, which affords a sense of richness. The design reflects the rich natural environment of Karuizawa so it can be loved and used for many years.

Between the two roofs, high-side windows allow natural light to flood into the hall, creating a bright space that can be used without artificial lighting. During the intermediate seasons, the high-side windows can be opened for “gravity” ventilation, which allows cool Karuizawa air to circulate with the aim of an environmentally friendly building design.

A simple structural system that creates a rich shape

Two simple, untwisted planes comprise the roof, which is cut into a leaf-like, organic shape that changes gracefully toward the eaves. The leaf-shaped plane structure was constructed using only commercially available laminated wood, and without using any special curved sections. By slightly adjusting the angles of the columns to align with the centerline curve, columns and beams intersect nearly vertically, enabling common hardware for connections and minimizing the use of custom-made hardware.

Double columns made of European red pine (120mm × 240mm) are arranged at 1,820mm intervals to match the scale of the plywood, creating a space divided into gentle, forest-like zones. By unifying the detail shapes of the short-hand cut joints, construction complexity was reduced, resulting in a structure that combines a spacious roof shape and rhythmic beam spacing within a limited budget and construction period.

Additionally, the building’s volume is efficiently utilized by locating the kitchen and staff rooms under the high roof, and installing HVAC equipment in the ceiling space beneath the low roof.

Project Details

Project name: Poppins Nursery school Karuizawa Kazakoshi
Purpose: Nursery school
Location（prefecture, city: Karuizawa, Kitasaku-gun, Nagano Prefecture
Site area: 2699.04 sqm
Total floor area: 494.46 sqm
Number of floors: 1
Eave height/max height: 6.3 m
Main structure: Wood
Completion month/year: November 2022

Credits:

Client name: Poppins Educare Inc.
Lead architect: Nikken Sekkei Ltd
Main scope: Nikken Sekkei Ltd (concept/development design, supervision consulting) + Seibu Construction Co., Ltd. (supervision)
Construction Contractor: Seibu Construction Co., Ltd.
Photo credit: Norihito Yamauchi