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“B” Occupancy Corridor Width

General Definition

  • IBC (International Building Code – USA)
    • The Minimum Required Corridor Width under the International Building Code (IBC) refers to the minimum clear width that a corridor must provide to allow safe and efficient movement of occupants, especially during emergencies.
  • BSL (Building Standards Law – Japan, 建築基準法)
    • The Minimum Required Corridor Width under Japan’s Building Standards Law (BSL, Article 119) establishes fixed minimum corridor widths based on building size, type, and function to ensure safe evacuation and accessibility.

Corridor width requirements ensure safe and efficient movement within buildings, especially during emergencies. Both IBC (USA) and BSL (Japan) establish minimum corridor width standards, considering factors like occupancy type, occupant load, accessibility, and fire safety.

IBC (USA) – Corridor Width Requirements

Under the International Building Code (IBC 2018, Section 1020.2), the minimum required width for corridors depends on the occupancy type and occupant load.

Key Requirements

  • Minimum Corridor Width for Most Occupancies
    • The general minimum width for corridors is 44 inches (1118 mm).
  • Reduced Corridor Width for Small Occupant Loads
    • If the corridor serves fewer than 50 occupants, the minimum width can be 36 inches (915 mm).
  • Increased Corridor Width for Certain Occupancies
    • Healthcare (Group I-2) & Educational (Group E) Buildings:
      • Minimum corridor width = 72 inches (1829 mm) in healthcare (hospitals, nursing homes) to accommodate beds and stretchers.
      • Minimum corridor width = 72 inches (1829 mm) in educational buildings (Group E) serving 100 or more occupants.
  • Fire Safety Considerations
    • Corridors serving as fire-rated exit access paths must comply with smoke-proof and fire-resistance ratings.
  • Accessibility Compliance (ADA & ICC A117.1)
    • Corridors must be designed to accommodate wheelchair maneuvering.
    • Minimum turning radius at corridor intersections = 60 inches (1524 mm) for wheelchair users.
  • Sprinklered Buildings & Corridor Width Reduction
    • In fully sprinklered buildings, fire-rated corridor requirements may be reduced in certain cases, but the width requirements remain unchanged.

Example Application in an Office Building

  • If an office corridor serves 60 occupants, it must be at least 44 inches wide.
  • If a small office corridor serves fewer than 50 occupants, it may be 36 inches wide.
  • In a hospital, corridors must be 72 inches wide to allow stretcher movement.

BSL (Japan) – Corridor Width Requirements

Japan’s Building Standards Law (BSL, 建築基準法, Article 119) establishes minimum corridor widths for different types of buildings.

Key Requirements

  • Minimum Corridor Width for Most Buildings
    • Corridors must be at least 90 cm (35.4 inches) wide in standard buildings.
  • Wider Corridors for Large Office Buildings & Public Facilities
    • In large office buildings, corridor width is often increased to 100 cm (39.4 inches) or more.
    • Certain public-use buildings require corridors ≥120 cm (47.2 inches) to ensure safe evacuation.
  • Fireproof & Barrier-Free Design Considerations
    • BSL enforces fireproof corridor designs in high-rise and high-occupancy buildings.
    • Barrier-free corridors must allow for wheelchair access and easy navigation for individuals with disabilities.
  • Corridor Width in Residential & Mixed-Use Buildings
    • In apartment buildings, corridors typically follow the 90 cm minimum rule, but emergency routes may require wider passageways.
  • Stricter Corridor Requirements in High-Rise Office Buildings
    • For high-rise buildings above 31 meters (10+ stories), wider corridors and fireproof partitioning may be required.

Example Application in an Office Building

  • In a Tokyo office building, standard corridors must be at least 90 cm wide.
  • In a large office building, corridors are often designed at 100 cm (39.4 inches) or more.

IBC (International Building Code – USA)

  • Under IBC 2018, Section 1005.7.1, exit doors may encroach into the required corridor width, but with specific limitations to ensure safe egress:
    • Maximum Encroachment When Fully Open:
      • Doors can encroach up to 7 inches (178 mm) into the required corridor width when fully open at 90 degrees.
      • This ensures that door swings do not significantly obstruct emergency evacuation routes.
  • Encroachment While Opening:
    • When swinging open, doors must not reduce the effective clear corridor width by more than one-half (50%) at any point.
    • This is to prevent excessive blockage of the corridor that could hinder movement during an emergency.
  • Accessibility Considerations:
    • Doors must not obstruct wheelchair maneuvering clearances, ensuring compliance with ADA and ICC A117.1 accessibility standards.

BSL (Building Standards Law – Japan, 建築基準法)

  • Japan’s Building Standards Law (BSL, Article 119) also regulates door encroachment into corridors to maintain safe and efficient evacuation routes.
    • Maximum Encroachment Allowed:
      • Exit doors must not reduce the effective corridor width by more than 20 cm (7.87 inches) when fully open.
      • This is similar to the IBC’s 7-inch (178 mm) encroachment limit.
  • Corridor Clearance Requirements:
    • BSL ensures that when doors are in any open position, there must still be enough clearance for at least one wheelchair user to pass through comfortably.
    • This aligns with Japan’s barrier-free design principles.
  • Fire Safety Considerations:
    • In fireproof corridors, doors are typically required to be recessed or sliding doors to avoid encroachment into escape paths.

IBC vs. BSL – Corridor Width Requirements

FeatureIBC (USA) – RequirementBSL (Japan) – Requirement
General Minimum Corridor Width44 inches (1118 mm)90 cm (35.4 inches)
Small Occupant Loads (<50 people)36 inches (915 mm)90 cm (35.4 inches)
Healthcare / Large Facilities Corridor Width72 inches (1829 mm)100-120 cm (39.4 – 47.2 inches)
Fire-Rated Corridor DesignRequired in high-rise buildingsRequired in high-rise & public buildings
Barrier-Free ComplianceADA / ICC A117.1 standardsUniversal design encouraged
Max. Exit Door Encroachment When Fully Open7 inches (178 mm)7.87 inches (200 mm)
Encroachment While OpeningCannot reduce corridor width by more than 50%Must maintain wheelchair clearance
Fireproof Corridor ConsiderationsAllowed, but cannot obstruct egressRecessed/sliding doors preferred
Accessibility ComplianceADA & ICC A117.1Barrier-free design required

Case Study

Corridor Width Design for an Office Building – Honolulu vs. Tokyo

Project Overview

  • A company is constructing a 5-story office building with a total corridor length of 40 meters per floor. The building is being developed in:
    • Honolulu, USA (IBC jurisdiction)
    • Tokyo, Japan (BSL jurisdiction)
  • The design team must ensure that corridor widths comply with both IBC (USA) and BSL (Japan) requirements.

Honolulu (IBC) Compliance

  • Challenge:
    • The original corridor design was 36 inches wide, which is acceptable for small offices but does not meet the 44-inch requirement for large office buildings.
  • Solution:
    • Increased corridor width to 48 inches (1220 mm) for comfort and accessibility.
    • Ensured 60-inch turn radius at intersections for wheelchair maneuverability.
    • Installed fire-rated partitions in corridors as required by IBC for high-rise offices.

Tokyo (BSL) Compliance

  • Challenge:
    • The original corridor width of 90 cm (35.4 inches) met BSL minimums, but for a large office, a wider corridor is preferred.
  • Solution:
    • Increased corridor width to 100 cm (39.4 inches) to improve circulation.
    • Ensured compliance with fireproof corridor design required for high-rise buildings.
    • Incorporated barrier-free accessibility features such as tactile guidance strips for visually impaired individuals.

Final Universal Design Approach for Both Locations

To ensure compliance with both IBC (Honolulu) and BSL (Tokyo), the project adopted a universal design strategy:

  1. Designed corridors at 100 cm (39.4 inches) wide, exceeding BSL’s 90 cm minimum and meeting IBC’s 44-inch requirement.
  2. Incorporated fire-resistant partitions in corridors for compliance with both IBC and BSL fire safety regulations.
  3. Installed tactile warning strips and visual signage for universal accessibility.
  4. Maintained at least a 60-inch (1524 mm) turning radius at corridor intersections for ADA and barrier-free compliance.

Comparison of Final Corridor Widths for Both Locations

Corridor TypeIBC Requirement (Honolulu, USA)BSL Requirement (Tokyo, Japan)Final Universal Design Solution
Standard Office Corridor44 inches (1118 mm)90 cm (35.4 inches)100 cm (39.4 inches)
High-Occupancy Office Corridor48 inches (1220 mm)100 cm (39.4 inches)100 cm (39.4 inches)
Healthcare / Large Facility Corridor72 inches (1829 mm)120 cm (47.2 inches)120 cm (47.2 inches)

Key Takeaways

  1. IBC corridor width requirements vary by occupancy type and occupant load, while BSL applies fixed width standards.
  2. BSL requires at least 90 cm (35.4 inches) for corridors, whereas IBC sets a minimum of 44 inches (1118 mm) for most office buildings.
  3. A universal design approach exceeding both requirements ensures a safer and more accessible building design for both Honolulu and Tokyo.

Global Approach

To harmonize corridor width standards globally, considering the International Building Code (IBC, USA) and the Building Standard Law (BSL, Japan), the following comprehensive recommendations are proposed for Group B occupancy:

  • General Minimum Corridor Width
    • Recommended Global Minimum: 44 inches (1120 mm)
    • Ensures comfortable circulation and aligns closely with IBC, slightly exceeding BSL requirements.
  • Minimum Corridor Width for Small Facilities
    • Recommended Global Minimum: 39 inches (1000 mm)
    • Suitable for smaller occupancies, balancing international standards.
  • Healthcare and Large Facility Corridor Width
    • Recommended Global Standard: 72 inches (1830 mm)
    • Provides adequate space for patient transfer and emergency equipment movement, matching IBC and exceeding BSL minimums for improved safety and functionality.
  • Fire-Rated Corridor Design
    • Corridors should adhere to fire-rating standards, maintaining unobstructed and clearly marked paths, incorporating fire-resistant construction.
    • Aligns with both IBC and BSL for safety and evacuation efficacy.
  • Maximum Door Encroachment (when Fully Open)
    • Recommended Global Maximum: 7 inches (180 mm)
    • This globally harmonizes both standards, facilitating consistent international applicability.
  • Encroachment While Opening Doors
    • Allow door encroachment not to exceed 7.87 inches (200 mm) into the corridor width during operation.
    • Ensures compliance with stricter BSL standards without compromising international functionality.
  • Accessibility and Barrier-Free Compliance
    • Universal design must comply with ADA and ICC A117.1 guidelines, integrating barrier-free principles consistent with both US and Japanese standards.
    • Clear maneuvering space must be maintained to facilitate accessible navigation for individuals with disabilities.

By implementing these recommendations, projects achieve broad international compliance, prioritize occupant safety, and promote inclusive usability and effective evacuation strategies across diverse global jurisdictions.

USA:

C.W. (1) * Corridor Width Minimum Required 44 in. (112 cm.)
C.W. (2) * Corridor Width when Door Fixed Open = (C.W. (1) – 7 in. (17.8 cm.)
C.W. (3) * Corridor Width During Door Open = (C.W.) / 2
D. Max. * Maximum Distance when Door Fixed Open = 7 in. (17.8 cm.) D.C. * Door Side Clearance = 18 in. (45.72 cm.) to 24 in. (60.96 cm.)

Japan:

C.W. (1) * Corridor Width Minimum Required 90 cm. (35.4 in.)
C.W. (2) * Corridor Width when Door Fixed Open = C.W. (1) – 20 cm. (7.9 in.)
C.W. (3) * Corridor Width During Door Open = Must Maintain C.W. (1)
D. Max. * Maximum Distance when Door Fixed Open = 20 in. (7.9 in.) D.C. * Door Side Clearance = 40 cm. (15.75 in.)

TABLE 1020.2 – MINIMUM CORRIDOR WIDTH

OCCUPANCYMINIMUM WIDTH (inches)
Any facility not listed in this table44
Access to and utilization of mechanical, plumbing or electrical systems or equipment24
With an occupant load of less than 5036
Within a dwelling unit36
In Group E with a corridor having an occupant load of 100 or more72
In corridors and areas serving stretcher traffic in ambulatory care facilities72
Group I-2 in areas where required for bed movement96

Note: For SI: 1 inch = 25.4 mm.

TABLE 1020.1 – CORRIDOR FIRE-RESISTANCE RATING

OccupancyOccupant Load Served by CorridorRequired Fire-Resistance Rating (hours)
Without Sprinkler System
H-1, H-2, H-3AllNot Permitted
H-4, H-5Greater than 30Not Permitted
A, B, E, F, M, S, UGreater than 301
RGreater than 10Not Permitted
I-2ᵃAllNot Permitted
I-1, I-3AllNot Permitted
I-4All1

Footnotes:

  • ᵃ: Separation not required where the building is equipped throughout with an automatic sprinkler system per Section 903.3.1.1.