The Ontario Building Code | Continuity of Fire Separations
3.1.8.3. Continuity of Fire Separations
(1) Except as permitted by Sentence 3.6.4.2.(2), a horizontal service space or other concealed space located above a required verticalfire separation, including the walls of a vertical shaft, shall be divided at the fire separation by an equivalent fire separation within the service space.
(2) The fire separation required by Sentence (1) shall terminate so that smoke-tight joints are provided where it abuts on or intersects,
(a) a floor,
(b) a roof slab, or
(c) a roof deck.
(3) Except as required by Subsection 3.6.3. for a shaft penetrating a roof assembly, a shaft, including an exitenclosure, that penetrates a fire separation, shall,
(a) extend through any horizontal service space or any other concealed space, and
(b) terminate so that smoke-tight joints are provided where the shaft abuts on or intersects,
(i) a floor,
(ii) a roof slab, or
(iii) a roof deck.
(4) The continuity of a fire separation shall be maintained where it abuts another fire separation, a floor, a ceiling, or an exterior wall assembly.
In Plain Language
Concealed spaces above a required vertical fire separation (like duct spaces above a wall) must themselves be divided at that same line by an equivalent fire separation, with smoke-tight joints where it meets floors, roof slabs, or roof decks, and shafts penetrating a fire separation have their own continuity requirements.
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.