The Ontario Building Code | Fire Blocks between Vertical and Horizontal Spaces
3.1.11.4. Fire Blocks between Vertical and Horizontal Spaces
(1) Fire blocksconforming to Article 3.1.11.7. shall be provided,
(a) at all interconnections between concealed vertical and horizontal spaces in interior coved ceilings, drop ceilings and soffits in which the exposed construction materials within the space have a flame‑spread rating more than 25, and
(b) at the end of each run and at each floor level in concealed spaces between stair stringers in which the exposed construction materials within the space have a flame‑spread rating more than 25.
In Plain Language
Fire blocks are required at interconnections between concealed vertical and horizontal spaces in coved ceilings, drop ceilings, and soffits, and at stair-stringer concealed spaces, wherever the exposed materials in those spaces exceed a 25 flame-spread rating.
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.