Title

Part 3 – Single egress for multi-unit residential buildings up to 6 storeys

Description

This request for change proposes additional sentences under NBC Div.B Section 3.4.2.1 to introduce single exit multi-unit residential buildings of up to six 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 – 3.4.2.1

Standing Committee(s)

Use and Egress, Fire Protection

Related CCR(s)

Part 9 – Single egress for multi-unit residential buildings up to 3 storeys (CCR 1815)

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

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

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 150 on the upper storeys of the building.

• no more than 4 dwelling units per storey, consistent with Seattle SBC 2018, 1006.3.3.7 Single Exits and NFPA 101 and NFPA 5000 model code conditions for single exit apartment buildings.

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

• Note: sprinklering is not a proposed measure for the Part 3 code change request, given the NBC already requires such buildings to be sprinklered throughout, however sprinklering to NFPA 13 is an upgrade where a four-storey building is otherwise permitted to be sprinklered to NFPA 13-R.

• requiring a smoke control measure for the single exit, unless an exterior exit stair or exterior passageway is provided, similar to the requirements for smoke control measures in high-rise buildings above 18m in building height (refer to 3.2.6.2. Limits to Smoke Movement and 3.2.6.6. Venting to Aid Firefighting).

• 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, and requiring automatic monitoring of the fire alarm system in conformance with 3.2.4.7. Signals to Fire Department,and requiring smoke detectors within dwelling units in lieu of smoke alarms to increase reliability of the occupant notification system.

• increasing the fire-resistance rating of the exit fire separation to increase reliability of the compartmentation of the single exit stair.

• limiting the flame spread rating of interior wall and ceiling finishes in public corridors to be the same as exits, whereas NBC 3.1.13.6 provides 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 1, Division B, Part 3 - Fire Protection, Occupant Safety and Accessibility
3.4.2. Number and Location of Exits from Floor Areas
3.4.2.1 Minimum Number of Exits

1) Except as permitted by Sentences (2) to (5), every floor area intended for occupancy shall be served by at least 2 exits.

2) A floor area in a building not more than 2 storeys in building height, is permitted to be served by one exit provided the total occupant load served by the exit is not more than 60, and

a) in a floor area that is not sprinklered throughout, the floor area and the travel distance are not more than the values in Table 3.4.2.1.-A, or
b) in a floor area that is sprinklered throughout
        i) the travel distance is not more than 25 m, and
        ii) the floor area is not more than the value in Table 3.4.2.1.-B.

3) Except as permitted by Sentence (4), if Sentence (2) permits a single exit from a floor area classified as Group B or Group C occupancy, the exit shall be an exterior doorway not more than 1.5 m above adjacent ground level.

4) The requirements of Sentences (1) and (2) are permitted to be waived for dwelling units that have an access to exit conforming to Sentences 3.3.4.4.(1) to (4).

5) A floor area classified as Group C occupancy in a building not more than 6 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) the building has a height not more than 18 m measured between the floor of the first storey and the uppermost floor level, excluding any floor level within a rooftop enclosure that is not considered as a storey in calculating building height in accordance with Sentence 3.2.1.1.(1),

b) 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,

c) 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,

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

e) the required fire alarm system is designed to notify the fire department that an alarm signal has been initiated, and smoke detectors are installed in lieu of smoke alarms within each dwelling unit,

f) unless an exterior exit stair is provided, or an interior or enclosed exit stair served by an exterior passageway is provided, the single exit facility shall be designed to limit the danger to occupants and firefighters from exposure to smoke in a building fire,

g) the single exit facility shall be separated from all other spaces in the building by a fire separation having a fire resistance rating not less than 1.5 h,

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

i) 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

i) 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 units.

6) Exits are not required directly from rooftop enclosures that are provided with access to exits in conformance with Sentences 3.3.1.3.(5) and (6).

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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

OS1 - Fire Safety
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 fire. The risks of injury due to fire addressed in this Code are those caused by—

OS1.2 - fire or explosion impacting areas beyond its point of origin

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

OP1 - Fire Protection of the Building
An objective of this Code is to limit the probability that, as a result of its design or construction, the building will be exposed to an unacceptable risk of damage due to fire. The risks of damage due to fire addressed in this Code are those caused by—

OP1.2 - fire or explosion impacting areas beyond its point of origin

NBC Div. A Part 3 - Functional Statements

F05     To retard the effects of fire on emergency egress facilities.

F06     To retard the effects of fire on facilities for notification, suppression and emergency response.

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

F12     To facilitate emergency response.

Supplement to the NBC 2015 - Intent Statements

NBC 3.4.2.1.(1). - OS3 Safety in Use - [F10, F12, F05, F06-OS3.7]
Intent 1: To limit the probability that persons will not have a choice of an alternative exit in the event that 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.

Intent 2: To limit the probability that emergency responders will not have a choice of an alternative exit in the event that one exit is blocked or obstructed in an emergency situation, which could lead to emergency responders being delayed in gaining access to a floor area, which could lead to delays or ineffectiveness in emergency response operations, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.

NBC 3.4.2.1.(1). - OS1 Fire Safety - [F12, F06-OS1.2]
Intent 1: To limit the probability that emergency responders will not have a choice of an alternative exit in the case of one exit being blocked or obstructed in a fire situation, which could lead to emergency responders being delayed in gaining access to a floor area, which could lead to delays or ineffectiveness in emergency response operations, which could lead to the spread of fire, which could lead to harm to persons.

NBC 3.4.2.1.(1). - OP1 Fire Protection of the Building - [F12, F06-OP1.2]
Intent 1: To limit the probability that emergency responders will not have a choice of an alternative exit in the case of one exit being blocked or obstructed in a fire situation, which could lead to emergency responders being delayed in gaining access to a floor area, which could lead to delays or ineffectiveness in emergency response operations, which could lead to the spread of fire, which could lead to harm to persons.

NBC 3.4.2.1.(2).
Intent 1: To exempt certain floor areas from the requirements of Sentences 3.3.1.3.(9) and 3.4.2.1.(1) concerning multiple exits and allow a single exit on the basis that the floor area served by the exit has a limited occupant load, and a restricted area and travel distance.

NBC 3.4.2.1.(4).
Intent 1: To exempt access to exits for dwelling units from the requirements of Sentence 3.4.2.1.(1) or (2), which would otherwise require two exits or one exit, provided some conditions are met, on the basis that:
- occupants are familiar with their egress routes, and
- the dwelling unit design will be constrained in accordance with Sentences 3.3.4.4.(1) to (4), thus limiting the number of occupants.


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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