About Non-Combustible Materials

— Performance Requirements for Interior Architecture and

the Principles Behind Realizing Wood-Based Design —

① Why Non-Combustible Materials Are Required for Interior Use

In architectural spaces, the requirement for non-combustible materials goes beyond simply being “hard to burn.”
Under the Building Standards Act of Japan, ensuring human safety during a fire and preventing the spread of flames are critical objectives. As a result, in buildings used by an unspecified number of people or in spaces above a certain scale, the fire performance of interior materials is strictly regulated.

Key concerns during a fire include:

  • Rapid heat release in a short period of time

  • Generation of smoke and toxic gases

  • Spread of fire from ceilings and walls that may obstruct evacuation

For this reason, interior materials are required not only to be visually appealing, but also to have controlled behavior in the event of a fire.

② What Are Interior Finish Restrictions?

Interior finish restrictions are regulations that limit the types of materials that can be used on walls and ceilings, depending on a building’s use, size, and structure.
These restrictions are defined under the Building Standards Act of Japan and related governmental notices.

For example, buildings such as:

  • Hotels

  • Commercial facilities

  • Hospitals and welfare facilities

  • Schools and public buildings

may be required to use non-combustible or quasi-non-combustible materials for walls and ceilings.

Ceiling finishes are often subject to stricter performance requirements than walls, as heat and smoke tend to accumulate near the ceiling during a fire.

③ Classification of Fire-Resistant Materials

(Non-combustible / Quasi-non-combustible / Flame-retardant)

Fire-resistant materials used under interior regulations are generally classified into three categories:

  • Non-combustible materials

  • Quasi-non-combustible materials

  • Flame-retardant materials

These classifications are not based on a simple binary distinction of “burning or not burning.”
Instead, evaluation focuses on fire behavior, including:

  • Heat release when exposed to fire over a specified period

  • Toxicity of smoke and gases

  • The manner in which combustion progresses

In design practice, it is essential to accurately identify which level of performance is required for the intended space.

④ Requirements for Non-Combustible Materials

To be certified as a non-combustible material, products must pass performance evaluation tests defined by national regulations.
Primary evaluation criteria include:

  • Extremely low heat release during combustion

  • No generation of hazardous gases during a fire

It is important to note that these evaluations focus on behavior during an emergency fire scenario—not under normal conditions of use.

Non-combustible materials can therefore be understood as materials that do not contribute to fire spread and do not obstruct evacuation or firefighting efforts when exposed to fire.

⑤ What Do the Tests Evaluate?

(Heat Release and Gas Toxicity)

The performance of non-combustible materials is verified through testing conducted by designated third-party testing organizations.

Typical evaluation items include:

  • The amount of heat generated when exposed to fire (heat release)

  • Whether toxic gases harmful to the human body are produced during combustion

These factors are assessed quantitatively, and only materials that meet defined criteria are certified as non-combustible.

Non-combustible certification serves as proof that both the material composition and test results comply with regulatory standards.

⑥ Why Solid Wood and Veneer Are Challenging as Non-Combustible Materials

Natural wood and veneer offer exceptional aesthetic qualities, but they are inherently organic materials.
Because wood is combustible by nature, it cannot be classified as a non-combustible material when used on its own.

As a result:

  • The use of wood is restricted in spaces subject to interior finish regulations

  • Designers may be forced to abandon wood-based designs despite strong aesthetic intent

To realize wood-based design within non-combustible requirements, a comprehensive material system must be designed to ensure non-combustible performance as a whole.

⑦ How TSUKI-ITA PANELS Address These Requirements

TSUKI-ITA PANELS are interior panels developed to preserve the expression of natural wood veneer while obtaining non-combustible material certification under the Building Standards Act of Japan.

Their non-combustible performance is achieved not by the veneer alone, but through:

  • A substrate with certified non-combustible performance

  • A surface layer of natural wood veneer

  • A carefully designed overall material composition

This structure enables the use of wood textures in spaces where non-combustible designation has traditionally been a barrier.

TSUKI-ITA PANELS

Not intended for mass production,
this material is created for designers who wish to engage deeply with the design intent of each individual project.

  • Ministerial Approval by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT): NM-6060

⑧ Volcanic Glass-Based Composite Board

To ensure stable non-combustible performance, TSUKI-ITA PANELS use a volcanic glass-based composite board as the core substrate.

This substrate is widely used in architectural applications because:

  • Its non-combustible performance is clearly defined

  • It has an extensive track record in the construction industry

By combining this non-combustible substrate with natural wood veneer, MORI KOUGEI achieves a balance between refined design expression and safety performance.