— Which Types and Sizes of Buildings Are Subject to Regulation—

In Japan, interior finish regulation is a legal requirement under the Building Standards Act that restricts interior finishing materials based on a building’s use, size, and location, in order to control fire spread and smoke during a fire.
In commercial and public projects, failing to confirm these requirements early often leads to costly redesigns later.

In interior design and renovation projects in Japan, the term “interior finish regulation” inevitably comes up at some point.
However, in practice, projects often proceed without a clear understanding of:

• Which buildings are subject to regulation
• Which specific areas are regulated
• Why certain finishes are prohibited

As a result, designers may later be told,

“That finish cannot be used,”

forcing major revisions at an advanced stage of the project.

This article explains the basics of interior finish regulation in Japan, focusing on
which building uses and scales are subject to regulation.

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What Is Interior Finish Regulation in Japan?

Interior finish regulation in Japan refers to rules that restrict interior finishing materials to limit fire spread and smoke development during a fire.

The regulation generally applies to:

• Walls
• Ceilings
• Fixed interior elements (built-in finishes)

Floor finishes are generally not subject to interior finish regulation.

An important point to understand is that
interior finish regulation in Japan does not apply uniformly to all buildings or all rooms.

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Key Factors That Determine Whether Regulation Applies

In Japan, whether interior finish regulation applies is mainly determined by the following three factors:

• Building use (occupancy classification)
• Building scale (floor area and number of stories)
• Location of the room (floor level, fire compartments, evacuation routes)

Among these factors, building use has the greatest impact.

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Building Uses Commonly Subject to Interior Finish Regulation in Japan

Interior finish regulation in Japan becomes stricter for buildings used by an unspecified or large number of occupants.

Typical examples include:

• Restaurants
• Retail stores
• Hotels and inns
• Hospitals and clinics
• Theaters and cinemas
• Amusement facilities (e.g., game centers)
• Schools and childcare facilities

These are categorized as “special buildings” under Japanese regulations and are far more likely to be subject to interior finish regulation than residences or standard offices.

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Regulation Varies Even Within the Same Use

Even for the same type of use—such as restaurants or retail stores—requirements differ depending on conditions such as:

• Small standalone street-level shops
• Tenants within large commercial complexes
• Basement floors or windowless spaces

Extra caution is required in Japan when a space is:

• Over a certain floor area
• Located underground
• Lacking sufficient openings or windows

In such cases, both walls and ceilings may be required to use non-combustible materials.

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Regulation May Apply Only to Part of a Building

One of the most confusing aspects in Japanese practice is that
interior finish regulation may apply only to specific areas, not the entire building.

Typical examples include:

• Common corridors
• Evacuation routes
• Rooms adjacent to fire compartments
• Specific rooms with designated uses

In these cases, designers may encounter requirements such as:

• Only ceiling finishes being regulated
• Only wall finishes being regulated

Careful judgment is required for each individual area.

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Interior Finish Regulation Does Not Eliminate Design Freedom

Interior finish regulation in Japan is often associated with reduced design flexibility, such as the assumption that:

“Wood finishes cannot be used.”

However, this is only partially true.

Today, many materials in Japan combine design quality and legal compliance, including:

• Non-combustible wood-look materials
• Non-combustible decorative panels
• Certified fire-resistant finish systems

The key is to design with interior finish regulation in mind from the very beginning.

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Items to Confirm at the Early Design Stage in Japan

To avoid redesign and delays later, the following items should be confirmed early in the design process:

• Official building use classification under Japanese law
• Target floor level (above ground or basement)
• Applicable floor area thresholds
• Relationship to common areas and evacuation routes

Clarifying these points first allows material selection and ceiling planning to proceed smoothly.

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Summary

• Interior finish regulation in Japan does not apply to all buildings
• Applicability depends on use, scale, and location
• Regulation may apply only to part of a building
• Early confirmation is critical to avoid redesign

Understanding interior finish regulation in Japan enables sound design decisions without unnecessary restrictions.

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Important Disclaimer

This article provides general information regarding interior finish regulation in Japan.
Actual requirements vary depending on building use, size, structure, local authority interpretations, and existing building conditions.

For final decisions, always consult the relevant local building authority, inspection agency, licensed architect, or other qualified professionals in Japan.