Typology
3-Storey Apartment Building

Occupancy
Group C, 10 Dwelling Units

Classification
2012 Ontario Building Code, Part 9

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Status: Submitted to City of Toronto (November 2024), Accepted by City of Toronto (May 2026)

A building permit application and alternative solution has been submitted to the City of Toronto for this three-storey small apartment building proposed to be constructed with a single exit stair and dwelling units opening into an exit lobby. The building contains two units on the ground floor, and four units on the second and third floor (total of 10 dwelling units and 25 bedrooms).

The zoning by-law allows for a small apartment building or a row of stacked townhouses (rowhouses with secondary suites) within the same overall lot coverage, setbacks and building depth on this site. Builders often prefer rowhouses because each unit has a separate entrance and the building is calculated as 100% saleable floor area. However, the client for this project is a community land trust and non-market housing provider looking to build accessible rental housing.

As a result of the single exit stair design, it becomes feasible to construct a small apartment building with 10 dwelling units served by an elevator within the same overall height and area as a row of 4 stacked townhouses.

A summary of the single exit stair alternative solution is provided below to describe the conditions for this 3-storey residential building compared to the minimum requirements for a prescriptive design of the same height and classification. The prescriptive requirement that will not be met by the design are OBC Setences 9.9.8.2.(2) and 9.9.8.5.(3). In lieu of complying with these prescriptive requirements, an alternative solution with mitigating measures addressing the Objectives and Functional Statements attributed to these requirements is proposed.

The single exit stair building design includes several conditions that would otherwise not be required for a three-storey small apartment building. Please note that the current edition of the United States model ‘International Building Code’ allows for a single exit serving R-2 occupancies in buildings of not more than three storeys in height with a maximum of four dwelling units per storey, provided that the building is sprinklered throughout. The NFPA (National Fire Protection Association) 101 Life Safety Code also allows a single exit serving R-2 occupancies in buildings of not more than four storeys in height with additional conditions.

The City of Toronto has also prepared a staff report, Item 2024.PH14.7 “Single Exit Stair: Ontario Building Code Feasibility Study” prepared by LMDG Building Code Consultants and adopted by city council on July 24, 2024 to address this topic.

Note: The original design and alternative solution was proposed to have dwelling units opening directly into the exit, and an elevator located in the exit. As part of the review process led by Toronto Buildings and Fire Services, the design was revised to provide a public corridor on the upper storeys and an exit lobby on the ground floor so that dwelling units and the elevator do not open directly into the exit stair.

Single Exit Stair (SES) Alternative Solution Proposal

- building fully sprinklered in accordance with NFPA 13

- fire separation of exit and between suites increased to 1-hour rating

- balconies provided to each dwelling unit on the upper storeys, sized in accordance with 3.3.1.7.(4) and located within reach of ground ladders

- performance of suite entry doors increased to 45-min leakage-rated smoke doors in accordance with NFPA 105

- exit facility width increased to 1200mm

- not more than 4 dwelling units per storey (consistent with NFPA 101 Life Safety Code and 2024 IBC)

2024 OBC Acceptable Solution (Part 9)

- building not required to be sprinklered (9.10.1.3.(8))

- fire separation of exit and between suites required to be 45-min (9.9.4.2.)

- balconies are not typically required (OBC 9.9.9.1.(3) does require a balcony in multi-storey dwelling units with one egress door)

- fire-protection rating of closures required to be 20-min (Table 9.10.13.1.)

- exit facility width not less than 900mm (9.9.3.2.)

- OBC 9.9.7.3. limits dead-end corridors to not more than 4 suites

“The typical European stair hall directly accessible from the surrounding apartments is a highly visible and familiar feature that the apartment dwellers know well. They know where it is and where it goes, both at the top and the bottom. It is not a mysterious construction at the nether ends of long corrridors, hidden behind heavy steel doors and populated by muggers. This may be an important safety feature...”

    - Gates, Blandford and Sandori, Paul. (1984). Fire Safety and the Design of Apartments,
A Report to the Canada Mortgage and Housing Corporation.https://assets.cmhc-schl.gc.ca/sf/project/archive/research/ca1_mh_84f38.pdf

These visualizations illustrate the original design with dwelling units opening direclty into the exit.

The public corridor provided as per the revised alternative solution is not shown here.