Title

Part 9 – Single egress for multi-unit residential buildings up to 3 storeys

Description

This request for change proposes additional sentences under NBC Div.B Section 9.9.8.2. to introduce single exit multi-unit residential buildings of up to three storeys, requiring additional life safety measures and placing limits on the occupant load and number of dwelling units per storey served by the single exit.

Proponent

Conrad Speckert
LGA Architectural Partners

David Hine
David Hine Engineering Inc.

Submitted

2022-04-18 (resubmitted 2025-03-08)

Code Reference(s)

NBC Div. B – 9.9.8.2

Standing Committee(s)

Housing and Small Buildings, Use and Egress, Fire Protection

Related CCR(s)

Part 3 – Single egress for multi-unit residential buildings up to 6 storeys (CCR 1816)

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Requested change/addition: What is the proposed solution and how does it address the problem?

Part 9 of the National Building Code of Canada should allow for a single means of egress in multi-unit residential buildings of up to three storeys above grade. A related CCR has been submitted for Part 3.

The code change request includes reasonable limitations and additional life safety measures informed by the intent statements and level of performance established by the acceptable solutions in the NBC, a review of building codes in other jurisdictions, as well as the attached reference literature and studies of fire safety in residential buildings:

• a limit of 30 occupants per storey served by a single exit stair, resulting in a cumulative permitted occupant load served by a single exit stair of 60 persons on the upper storeys of the building, consistent with NBC 9.9.8.2.(2).

• no more than 4 dwelling units per storey, consistent with the 2015 IBC, 1006.3.2 Single Exits, the NFPA 101 and NFPA 5000 model code conditions for single exit apartment buildings and Ontario (OBC) specific limits on dead-end corridors.

• a maximum floor area of 150m² per dwelling unit, consistent with 2020 NBC Table 3.4.2.1.-B for sprinklered floor areas and a maximum travel distance within dwelling units of 25 metres, consistent with 2020 NBC 3.4.2.1.(2)(b)(i).

• requiring sprinklering throughout the building to NFPA 13.
  

• increasing the minimum fire-resistance rating of fire separations and loadbearing assemblies from 45-min to 1 hour to improve reliability of the compartmentation.
  

• increasing the minimum fire-protection rating of dwelling unit entrance closures from a 20-min rating to a 45-min rating, similar to the closure ratings required by several other jurisdictions.

• requiring a fire alarm system without exception ( which is also required by sprinklering the building) and requiring smoke detectors within dwelling units in lieu of smoke alarms to increase reliability of the occupant notification system.

• limiting the flame spread rating of interior wall and ceiling finishes in public corridors to be the same as exits, whereas NBC 9.10.17.2. and 9.10.17.5. provide exceptions for sprinklered floor areas.
  

Additional life safety measures that may be appropriate to add:

• requiring sprinklering of balconies, if provided, based on Calder and Senez’s 2016 study of “The Key Modes of Fire Spread in Wood-Framed Apartment Buildings.”
  

National Building Code of Canada, Volume 2, Division B, Part 9 - Housing and Small Buildings
9.9.8. Exits from Floor Areas
9.9.8.2 Number of Required Exits

1) Except as provided in Sentences (2) and (3) and Subsection 9.9.9., at least 2 exits shall be provided from every floor area, spaced so that the travel distance to the nearest exit is not more than

a) 40 m in the case of business and personal services occupancies,

b) 45 m for all occupancies where the floor area is sprinklered, and

c) 30 m for all other occupancies.

2) Except as provided in Subsection 9.9.9., a single exit is permitted from each storey in buildings of 1 and 2 storeys in building height provided the floor area and travel distance requirements conform to those required in Article 9.9.7.4. and the total occupant load served by an exit facility does not exceed 60 persons.

3) A floor area classified as Group C occupancy in a building not more than 3 storeys in building height is permitted to be served by a single exit provided the occupant load per storey served by a single exit does not exceed 30 persons, and

a) a single exit serves not more than four dwelling units per storey and the floor area of each dwelling unit served by a single exit does not exceed 150m²,

b) the travel distance within any suite served by a single exit is not more than 25 m and the travel distance from the egress door of any suite to the single exit is not more than 6 m,

c) the building is sprinklered throughout with an automatic sprinkler system designed, constructed, installed and tested in conformance with NFPA 13,

d) a fire alarm system is installed without exception and smoke detectors are installed in lieu of smoke alarms within each dwelling unit,

e) the fire-resistance rating of fire separations and loadbearing assemblies except roofs is not less than 1 h,

f) the fire-protection rating of suite entry doors is not less than 45 min,

g) the maximum flame-spread rating of 90% of interior wall and ceiling finishes in any sprinklered public corridor served by a single exit shall be not more than 25, and

h) the floor area classified as Group C occupancy served by a single exit is not intended for use a retirement home, hostel, hotel, dormitory or any residential use other than dwelling.

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Objective(s): Which of the stated objectives and functional statements of the Code will the proposed solution assist in achieving?

The Functional Statement and Objective attributions to existing sentences may not have to be changed. The attributions to the new Article being introduced may be made up of the following selection, which is consistent with the code provisions the CCR complements:

NBC Div. A Part 2 - Objective Statements

OS3 - Safety in Use
An objective of this Code is to limit the probability that, as a result of the design or construction of the building, a person in or adjacent to the building will be exposed to an unacceptable risk of injury due to hazards. The risks of injury due to hazards addressed in this Code are those caused by—

OS3.7 - persons being delayed in or impeded from moving to a safe place during an emergency

NBC Div. A Part 3 - Functional Statements

F10     To facilitate the timely movement of persons to a safe place in an emergency.

Supplement to the NBC 2015 - Intent Statements

NBC 9.9.8.2.(1). - OS3 Safety in Use - [F10-OS3.7]
Intent 1: To limit the probability of excessive travel distances to exits, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.

Intent 2: To limit the probability that persons will not have access to an alternative exit in the event one exit is blocked or obstructed in an emergency situation, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.

NBC 9.9.8.2.(2).
Intent 1: To supersede the requirements of Sentence 9.9.8.2.(1), which would otherwise require at least 2 egress routes or exits, and permit a single exit, on the basis that the single exit is limited to low buildings having a relatively low occupant load and where floor areas and travel distances are limited.


Emergency
The term “emergency” — in the context of safety in buildings — is often equated to the term “fire emergency;” however, the wording of objectives OS3.7 and OS5.9 makes it clear that the Code addresses any type of emergency that would require the rapid evacuation of the building, such as a bomb threat or the presence of intruders.

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