Typology
3-Storey Triplex

Occupancy
Group C, 3 Dwelling Units

Classification
2024 Ontario Building Code, Part 9

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Status: Submitted for Building Permit (December 2024), Approved by City of Toronto (April 2025)

A building permit application and alternative solution has been submitted to the City of Toronto for a three-storey triplex proposed to be constructed with a single exit stair. The building is located on a narrow 4.7m (15’ 5”) wide lot and contains a total of three one-bedroom dwelling units.

As a result of the single exit stair design, it becomes feasible to construct a triplex where only a duplex or a house with a secondary suite would otherwise be feasible.

The second and third storey dwelling units (Unit 2 and 3) share access into a single exit stair. The single exit stair discharges at the ground floor directly to the exterior. The proposed building does not comply with Sentence 9.9.9.3.(1) since only one exit is proposed from each dwelling unit.

Note: It is not feasible to provide a second means of egress as an unenclosed exterior exit stair at the back of the building because the rear yard does not have access to a public thoroughfare and the property is too narrow to accomodate a side yard setback to access the street.

The alternative solution is summarized as follows:

Single Exit Stair (SES) Alternative Solution

- building sprinklered to NFPA 13-R standard

- building equipped with a fire alarm system having smoke detection in the exit stair and smoke detectors in lieu of smoke alarms in each suite

- fire separation of exit increased to 1h fire-resistance rating and fire-protection rating of closures increased to 45-min. Suite entry doors to be weatherstripped to mitigate risk of smoke spread beyond suite of origin.

- flame-spread rating of 100% of interior finishes in exit limited to FSR 25 (walls, ceiling and floors)

- exit facility width increased to 1100mm

2024 OBC Acceptable Solution (Part 9)

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

-  fire alarm system not required for residential occupancy where an exit serves not more than 4 suites (9.10.18.2.(2))

- fire separation of exit required to be 45-min (9.9.4.2.) and fire-protection rating of closures required to be 20-min (Table 9.10.13.1.) and solid core wood doors and unrated wood door frames permitted (9.10.13.2./3.).

- flame-spread rating of 90% of ceiling and walls in an exit limited to 25 (9.10.17.)

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