The Ontario Building Code | Scope
3.4.7.1. Scope
(1) Except as permitted by Sentence (2), fire escapes shall not be erected on a building.
(2) If it is impracticable to provide one or more of the exit facilities listed in Article 3.4.1.4., fire escapes conforming to Articles 3.4.7.2. to 3.4.7.7. are permitted to serve floor areas in an existing buildingprovided the floor areas served are,
(a) not in an elementary or secondary school,
Note: On July 1, 2017, Clause 3.4.7.1.(2)(a) of Division B of the Regulation is amended by adding "or a retirement home" at the end. (See: O. Reg. 139/17, s. 44)
(b) not more than 2 storeys above ground level in care, care and treatment or detention occupancies, and
(c) not more than 5 storeys above ground level in other occupancies.
In Plain Language
Fire escapes generally can't be erected on a building at all; they're only permitted on existing buildings where providing another exit facility type is impractical, and even then subject to conditions like not serving a school.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.