004_Concrete–Timber Hybrid Detail Section

Location : Japan
Type : Wall Assembly
Year : 2024

In Japan, a detailed section drawing is called a kanabakari-zu.
The term kanabakari originates from the name of a traditional carpenter’s tool used by Japanese builders, and refers to a technique for studying and calculating the sectional dimensions of a building.

Through this system, carpenters determine elements such as roof pitch, the projection of the eaves, and the heights of columns and beams.
It allows them to examine issues of form, space, and structural components in an integrated manner.

At the same time, it is a method for determining the scale of space and the overall proportion of a building, and it was considered an essential and systematic technique in traditional Japanese architecture.

Traditional Japanese buildings are often admired for the beauty of their proportions.
The kanabakari-zu—a sectional detail drawing that expresses these relationships—can therefore be considered one of the most important drawings in the design of a building.

In contemporary architecture, the sectional detail drawing also plays an important role in studying the assemblies required for building services, waterproofing, drainage, and insulation, and in illustrating how these systems are integrated into the building.
Thinking through a kanabakari-zu, which cuts across architecture, structure, and building services, is essentially equivalent to thinking about the building as a whole.
For this reason, the kanabakari-zu speaks eloquently about the intentions of a building.

This house is composed of a hybrid structure.
The first floor is formed by a concrete volume with exposed concrete exterior walls, while a white wooden cube forming the second floor projects above it.

In fact, many Japanese timber houses can be considered hybrid structures in a certain sense.
Although the superstructure is made of wood, the foundations are typically constructed of reinforced concrete.
These foundations protect the timber structure from ground conditions and provide a stable interface between the building and the earth (see “003_Wall–Ground Interface” for further explanation).
In that sense, this building could also be interpreted as a house placed on an enlarged foundation.

A lifted white house.
It may recall, in some ways, the spirit of modern architecture.
Le Corbusier once described architecture as a way to “liberate the building from the ground.”

However, this building does not liberate the ground.
It is not lifted by pilotis; rather, the building rises because the foundation itself becomes enlarged.

Since the ground is not freed beneath it, a space enclosed by concrete walls is created below.
These spaces function primarily as back-of-house areas such as storage rooms and service spaces.
The ceiling height here does not need to be very high.

Light enters modestly from the sides or filters down through stairs and voids.
The noise of the street is barely audible.
Together with the depth created by the mound and retaining walls outside, the atmosphere evokes the quietness and security of an underground space or a cave.

The upper floor, by contrast, is constructed in timber.
Natural light enters every room from the courtyard, creating a bright and light atmosphere.
The sloping roof allows the ceiling to rise, giving the interior a generous sense of openness.
Although there are no windows on the outer walls, the space does not feel oppressive.

Perhaps this is because one arrives here after moving up from the cave-like space below.
The sky, framed by the eaves of the courtyard, feels surprisingly close.

In this way, the house contains two contrasting spatial conditions within a single dwelling.
This contrast is made possible by the hybrid structure.

And it was the kanabakari-zu—the sectional detail drawing—that played a central role in examining these relationships.
Because it cuts across multiple aspects of architecture, it allows the story of the building as a whole to emerge.
The kanabakari-zu holds that kind of potential.

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