General Definitions:
- IBC (International Building Code, USA):
- Table 803.11 mandates the use of Class A or Class B fire-retardant interior finish materials depending on occupancy and location (e.g., exit enclosures, corridors).
- These classifications are based on ASTM E84 flame spread and smoke-developed indexes.
- BSL (Building Standard Law, Japan):
- Article 35 requires Class A (難燃材料) fire-retardant materials for interior wall and ceiling finishes in high-rise office buildings to minimize flame spread and smoke generation.
Comparison Table:
| Criterion | IBC (USA) | BSL (Japan) |
| Interior Finish Requirement | Class A or B materials based on occupancy and location | Class A (難燃材料) required in high-rise office walls and ceilings |
| Basis for Classification | Flame spread index (0–25 for Class A, 26–75 for Class B) | National standards defining flame resistance and smoke emission |
| Scope of Application | Applies to exits, corridors, and general interior spaces | Applies to walls and ceilings in high-rise office buildings |
| Compliance and Enforcement | Verified via ASTM E84 or NFPA 255 testing | Enforced nationally through JIS-based inspection systems |
| Flexibility and Adaptability | Prescriptive and performance-based allowances | Strict application in defined high-risk structures |
| Testing and Certification | ASTM E84 / NFPA 255 compliance | Japanese Industrial Standards (JIS) for interior finishes |
Key Differences:
- IBC: Offers flexibility with Class A or B options based on occupancy type and building area.
- BSL: More stringent in high-rise offices, requiring only Class A (難燃) materials.
Case Study:
5-Story Office Building
- Honolulu, USA (IBC):
- Interior Finishes: Class A or B permitted based on corridor or exit designation.
- Toyosu, Japan (BSL):
- Interior Finishes: Class A required for all wall and ceiling finishes in high-rise structures.
Global Approach:
- Unified Material Classifications:
- Standardize classification systems based on international flame spread indexes.
- Risk-Based Application Guidance:
- Require Class A in high-risk areas like exits and high-rises, allow Class B in low-risk interior zones.
- International Compliance and Labeling:
- Harmonize ASTM and JIS standards for fire-retardant material certification.
- Global Industry Education:
- Train architects, designers, and specifiers on selection and verification of fire-retardant finishes.
- Periodic Review and Research Integration:
- Convene international panels to revise classifications as materials science evolves.
Interior Wall and Ceiling Finish Requirements by Occupancy Group
(IBC Table 803.13 with Footnotes)
| Occupancy Group | Interior Exit Stairways, Ramps, and Exit Passageways (Sprinklered) | Exit Access Corridors and Ramps (Sprinklered) | Rooms and Enclosed Spaces (Sprinklered) | Interior Exit Stairways, Ramps, and Exit Passageways (Non-Sprinklered) | Exit Access Corridors and Ramps (Non-Sprinklered) | Rooms and Enclosed Spaces (Non-Sprinklered) |
|---|---|---|---|---|---|---|
| A-1 & A-2 | B⁽ᵃᵇ⁾ | B | C⁽ᶜ⁾ | A⁽ᵃᵇ⁾ | A⁽ᵈ⁾ | B⁽ᶜ⁾ |
| A-3⁽ᶠ⁾, A-4, A-5 | B⁽ᵃᵇ⁾ | B | C⁽ᶜ⁾ | A⁽ᵃᵇ⁾ | A⁽ᵈ⁾ | C⁽ᶜ⁾ |
| B, E, M, R-1 | B⁽ᵃᵇ⁾ | C⁽ᵐ⁾ | C⁽ᶜ⁾ | A⁽ᵃᵇ⁾ | B | C⁽ᶜ⁾ |
| R-4 | B⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ | A⁽ᵃᵇ⁾ | B | B |
| F | C⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ | B⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ |
| H | B⁽ᵃᵇ⁾ | B | C⁽ᵍ⁾ | A⁽ᵃᵇ⁾ | A | B |
| I-1 | B⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ | A⁽ᵃᵇ⁾ | B | B |
| I-2 | B⁽ᵃᵇ⁾ | B | B⁽ʰⁱ⁾ | A⁽ᵃᵇ⁾ | B | B⁽ʰⁱ⁾ |
| I-3 | A⁽ᵃᵇ⁾ | A⁽ʲ⁾ | C⁽ᶜ⁾ | A⁽ᵃᵇ⁾ | A | B |
| I-4 | B⁽ᵃᵇ⁾ | B | B⁽ʰⁱ⁾ | A⁽ᵃᵇ⁾ | B | B⁽ʰⁱ⁾ |
| R-2 | C⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ | B⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ |
| R-3 | C⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ | C⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ |
| S | C⁽ᵃᵇ⁾ | C | C⁽ᶜ⁾ | B⁽ᵃᵇ⁾ | B | C⁽ᶜ⁾ |
| U | No restrictions | No restrictions | No restrictions | No restrictions | No restrictions | No restrictions |
Footnotes:
- a: Interior finish in enclosed exit stairways and ramps must comply with this classification.
- b: Includes exit passageways.
- c: Applies to finishes on walls and ceilings of rooms and enclosed spaces.
- d: In Group A occupancies with fixed seating (like theaters), Class A is required.
- e: Not shown in table but used in related commentary for Group B examples (e.g., offices, banks).
- f: Group A-3 places of religious worship may qualify for less restrictive finish.
- g: Class C allowed in Group H occupancies under certain conditions.
- h: Class B required in patient rooms of Group I-2 and I-4.
- i: This rating applies to walls only, not ceilings.
- j: In Group I-3 housing, Class B permitted.
- m: Specific modification for Group E (educational facilities).
The BSL categorizes interior finishing materials into three main classes:
- Noncombustible materials (NC):
- Materials that do not burn when exposed to heat from a standard fire.
- Quasi-noncombustible materials (Q-NC):
- Materials that have limited combustibility under fire conditions.
- Fire-retardant materials (FR):
- Materials that can withstand fire exposure for a specified duration without significant combustion.
These classifications are determined based on the materials’ performance when heated during testing, including factors such as resistance to burning, deformation, melting, cracking, and the generation of smoke or harmful gases. The required classification for interior finishes depends on the building’s purpose and characteristics. For example, buildings with specific uses or larger scales may be required to use noncombustible materials for interior walls and ceilings to ensure a higher level of fire safety.IIBH
- Additionally, the BSL imposes restrictions on the use of formaldehyde-emitting materials for interior finishes to maintain indoor air quality.
- Materials are categorized based on their formaldehyde emission levels, and their usage is regulated accordingly to protect occupants’ health.日本建築センター
- The Japanese BSL provides comprehensive guidelines for interior wall and ceiling finishes, focusing on fire resistance and indoor air quality, akin to the standards set by the IBC.