Canada Builds

Means of Egress

There are three distinct definitions concerning the topic of egress and these are defined in OBC As a general rule, the intent of the building code is to ensure that a minimum standard is maintained with regards to the ability of any occupant to exit the building safely from anywhere in the building at any time. That is the objective. Providing for this objective to be met properly can be a complicated and often time consuming activity – both in design and construction. Consider the three main definitions for egress:


  1. Exit
  2. Access to Exit
  3. Means of Egress


A diagram to describe these three conditions for a typical 2 or 3 storey building requiring 2 exits shows the hierarchical order in which means of egress are considered. As a rule, means of egress is from ‘anywhere in the building’. An access to an exit is a protected path where the potential ‘crush’ or large and immediate congregation of persons might occur. (I.e. a corridor). A corridor is not the only kind of access to exit but it is the most common.

Figure 1                               Diagram showing egress conditions

An exit from any floor area shall be one of the following used singly or in combination:

  1. an exterior doorway
  2. an exterior passageway
  3. an exterior ramp
  4. an exterior stairway
  5. a fire escape
  6. a horizontal exit
  7. an interior passageway
  8. an interior ramp, or
  9. an interior stairway

Access to Exits

As a general rule, each suite in a floor area occupied by more than one suite shall have

  1. an exterior exit doorway, or
  2. a doorway to a public corridor or to an exterior passageway


Where the doorway enters a public corridor or exterior passageway it shall be possible to go in two directions to reach an exit. The exception to this rule is indicated in article Dead End Corridors. This article provides for the maximum conditions for dead end corridor lengths based on the occupancy served

Figure 2                               Exit Diagram

Measurement of Travel Distance (

Subsection 9.9.8. defines travel distance as the distance from any point in the floor area to an exit measured along the path of exit travel. The following is a summary of maximum travel distances permitted in Sentence

Occupancy                                          Not Sprinklered     Sprinklered

Business and Personal Service          40m (131 ft.)          45m (148 ft.)

Other Occupancies                             30m (98 ft.)            45m (148ft.)


The point at which this measurement for travel distance may be taken is further described in Sentence – where a room or suite is separated from the remainder of the floor area by a fire separation having a fire-resistance rating of at least 45 min, or in a sprinklered building, by a fire separation which is not required to have a fire-resistance rating, the travel distance is permitted to be measured from an egress door of the room or suite to the nearest exit


Number of Required Exits (

A single exit from a storey is permitted where:

Building does not exceed two storeys and conforms to floor area, travel distance and occupant load calculations described in


1.      Describe the conditions where a single exit is permitted from a Part 9 building

OBC Reference:



2.      As a general rule, how is Travel distance measured?
OBC Reference:

3.      What conditions need to be satisfied in order to avoid measuring the travel distance from the most remote point in a building to an exit?

OBC Reference:

Flame Spread Ratings

Flame Spread Rating is defined as an index or classification indicating the extent of spread of flame on the surface of a material or an assembly of materials as determined in accordance with articles and When reading these articles it should be understood that the general rule and intent is to limit flame spread in areas and pathways that would lead occupants to a safe egress from a building. The following is a list of requirements from Part 9 related to flame spread ratings (FSR)


OBC Reference    Description            Testing            Cut surfaces               Compartmentation of concealed spaces               Interior finishes, general rule              Ceilings in exits or public corridors              Walls in exits               Exterior exit passageways               Walls in public corridors               Interior finishes for occupancies in public corridors or corridors used by the public               Light diffusers and lenses             Foamed plastic wall or ceiling finish in combustible construction


Flame Spread Rating of Interior Surfaces

As a general rule the exposed surface of every interior wall and ceiling, including skylights shall have a surface flame spread rating of not more than 150. Doors within dwelling units do not need an assigned Flame Spread Rating. Other doors require FSR of 200.

Flame Spread Rating for Ceilings in Exits

At least 90% of the exposed surface of every ceiling in a public corridor shall have a surface flame spread rating of not more than 25. OBC excludes certain items from the calculation of ceiling area. These are skylights, glazing, combustible doors, and combustible light diffusers and lenses shall not be considered in the calculation of wall and ceiling areas

Flame Spread Rating for Walls in Exits

90% of the exposed surfaces of every wall in an exit shall have a surface flame spread rating of not more than 25. For lobbies this percentage is reduced to 75% of the wall area with an FSR of 25 (OBC

Flame Spread Rating for Walls in Corridors

90% of the total wall surface in any unsprinklered public corridor shall have a surface flame spread rating of not more than 75 or at least 90% of the upper half of such walls shall have a surface flame spread rating of not more than 25.

Flame Spread Rating Chart

Area                                                    FSR

Interior Surfaces                                  150

Doors                                                  200

Ceilings in Exits                                   25 (over 90% of the area)*

Walls in Exits                                       25 (over 90% of the area)*

Walls in Lobbies used as Exits            25 (over 75% of the area)*

Walls in Public Corridors                     75 (over 90% of the area) OR

Walls in Public Corridors                     25 (over 90% of the upper half of the walls)*

Walls and Ceilings in Bathrooms        200

Doors within dwelling units                  Unassigned


* Note: Skylights, glazing, combustible doors, and combustible light diffusers and lenses shall not be considered in the calculation of wall and ceiling areas


When reading into the requirements for Flame Spread Ratings be sure to verify that the term ‘surface flame spread is used. For instance, if the reference is to the required Flame Spread Rating only and not the ‘surface’ Flame Spread Rating then the Requirements also apply to the material if it were cut through. Flame Spread Rating

This article makes a reference to Part 3 and the Supplementary Guidelines. The article states that where a flame spread rating is required it shall be determined in accordance with the test methods in Part 3 or the Supplementary Guidelines. Read to find 2choices in determining the FSR of various materials

  1. Determined on the basis of not less than three tests conducted in conformance with CAN/ULC-S102.2)-M, “Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies”. The same standard is also in place for floors but bear in mind that floors are not assigned a required FSR until the building is considered ‘high’ according to 3.2.6. So unless the building is a ‘high building’ floors need not be given a FSR
  2. The second allowable method is to determine the FSR using the Supplementary Guidelines (SG-2). This method is easier.

Smoke Development Classification

Another important consideration to be made with FSR is the Smoke Development classification. This is an index on the general tendency of a material to propagate smoke under heated or flame conditions. Part 9 does not explicitly refer to the Smoke Development Classification of interior finishes. These are identified however in SG-2 along side the Flame spread ratings for various materials