Traditional Japanese wooden construction—known as the post-and-beam method (Zairai Kōhō)—is built using three main structural elements:
Posts (vertical)
Beams (horizontal)
Bracing (diagonal)
Understanding these components makes it much easier to judge:
- Which walls can be removed
- How high the ceiling can be raised
- How much flexibility a renovation allows
This knowledge is especially useful for hotel renovations, shop fit-outs, and residential remodeling.
1. Posts｜Vertical members that support the building
Posts transfer the weight of the roof and upper floors down to the foundation.
- Key structural elements carrying vertical loads
- Commonly spaced at 910 mm intervals (traditional Japanese module)
- Load-bearing posts generally cannot be removed
Posts function like the “legs” of the building.
Whether you can modify or relocate them greatly affects renovation flexibility.
2. Beams｜Horizontal members that carry loads across spans
Beams connect posts and support the load of floors and roofs.
- Usually hidden above the ceiling
- The position of the beam determines the maximum possible ceiling height
- Cutting or weakening a beam compromises structural safety
When planning to raise a ceiling, identifying the beam layout is one of the first and most important steps.
3. Bracing (Suji-kai)｜Diagonal members that resist earthquakes
Bracing provides lateral resistance against horizontal forces such as earthquakes and strong winds.
- Typically installed at 45° or 60°
- Reduces deformation during shaking
- Walls containing bracing are structural (shear) walls and cannot be removed without reinforcement
When determining whether a wall can be taken down,
the presence of bracing is often the deciding factor.
4. Two types of walls: “Ōkabe (Large Wall)” and “Shinkabe (Exposed Frame)”
The finishing system used on walls greatly affects how the structure is hidden or expressed—and how easy it is to renovate.
● Ōkabe (Large Wall / Concealed Frame)
This is the modern standard method in which posts and beams are covered by wall finishes.
- Clean, modern appearance
- Easy to install insulation and electrical wiring
- Greater design flexibility—finishes can be applied anywhere
- Easier to adjust room layouts or change door/window locations
- Because the structure is hidden, internal members cannot be confirmed visually
→ When structural confirmation is needed,
partial opening of the wall may be performed.
This is common for older buildings or when drawings are unavailable.
● Shinkabe (Exposed Frame Wall)
Used in traditional Japanese interiors such as tatami rooms.
- Posts and beams are visible, making structural layout easy to understand
- Ideal for traditional Japanese aesthetics
- Less freedom for insulation and wiring routes
Because the structure is exposed,
renovation decisions (such as wall removal) are easier to evaluate.
5. How these three elements work together
- Posts handle vertical loads
- Beams carry loads horizontally
- Bracing resists lateral forces such as earthquakes
Together they form a stable, three-directional structural system—
one of the reasons Japanese wooden buildings perform well in seismic conditions.
6. Practical points for renovation
- Always check whether bracing exists in a wall
- Modifying posts or beams requires proper structural reinforcement
- For Ōkabe (concealed frame) walls, structural members cannot be seen, so
partial opening may be necessary to inspect inside - Older buildings or ones without drawings often require direct on-site confirmation
In practice, professionals combine initial assumptions with
physical inspection to make safe and accurate decisions.
Summary
Understanding the basics of Japanese post-and-beam construction becomes easier once you remember:
- Posts = vertical load-bearing members
- Beams = horizontal structural members
- Bracing = diagonal elements resisting earthquakes
- Ōkabe = concealed wall with high design flexibility
- Shinkabe = exposed structure that is easy to evaluate visually
This foundational knowledge will help you navigate renovation planning with much more confidence.
【Required English Disclaimer】
This article provides general construction information for educational purposes.
Actual building conditions vary based on age, region, design, and construction quality.
Always consult licensed architects or structural engineers before removing walls or altering structural elements.
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