Code Library › Volume 1 › Section 3.1 — General
PART 3 — FIRE PROTECTION, OCCUPANT SAFETY AND ACCESSIBILITYUpdated for the 2024 Ontario Building Code

3.1.11.5.Fire Blocks in Horizontal Concealed Spaces

(1) Except for crawl spaces conforming to Sentence 3.1.11.6.(1) and as required in Sentence (3), horizontal concealed spaces within a floor assembly or roof assembly of combustible construction, in which sprinklers are not installed, shall be separated by construction conforming to Article 3.1.11.7. into compartments (a) not more than 600 m2 in area with no dimension more than 60 m, if the exposed construction materials within the space have a flame-spread rating not more than 25, and (b) not more than 300 m2 in area with no dimension more than 20 m, if the exposed construction materials within the space have a flame-spread rating more than 25. (See Note A-3.1.11.5.(1)) (2) A concealed space in an exterior cornice, a mansard style roof, a balcony or a canopy in which exposed construction materials within the space have a flame-spread rating more than 25, shall be separated by construction conforming to Article 3.1.11.7. (a) at locations where the concealed space extends across the ends of required vertical fire separations, and (b) so that the maximum dimension in the concealed space is not more than 20 m. (3) Except as provided by Sentence (5), in buildings or parts thereof conforming to Article 3.2.2.51. or 3.2.2.60., horizontal concealed spaces within a floor assembly or roof assembly of combustible construction shall be separated by construction conforming to Article 3.1.11.7. into compartments that are (a) not more than 600 m2 in area with no dimension more than 60 m, if the exposed construction materials within the space have a flame-spread rating not more than 25, and (b) not more than 300 m2 in area with no dimension more than 20 m, if the exposed construction materials within the space have a flame-spread rating more than 25. (See Note A-3.1.11.5.(3) and (4)) r1 (4) Except for crawl spaces conforming to Sentence 3.1.11.6.(1) and except as provided in Sentence (5), in buildings or parts thereof conforming to Article 3.2.2.48., 3.2.2.57. or 3.2.2.93., horizontal concealed spaces within a floor assembly or roof assembly of encapsulated mass timber construction shall be separated by construction conforming to Article
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.