National Building Code of Canada - Section 937

9.10.16.4. Division B 2) Fire blocks are deemed to comply with Sentence (1) if they are constructed of not less than a) 0.38 mm sheet steel, b) 12.7 mm gypsum board, c) 12.5 mm plywood, OSB or waferboard, with joints having continuous supports, d) two layers of lumber, each not less than 19 mm thick, with joints staggered, or e) 38 mm lumber. 3) In a building permitted to be of combustible construction , semi-rigid fibre insulation board produced from glass, rock or slag is permitted to be used to block theverticalspaceinadouble-framewallassemblyformedattheintersectionofthe floor assembly and the walls, provided the width of the vertical space does not exceed 25 mm and the insulation board a) has a density not less than 45 kg/m 3 , b) is securely fastened to one set of studs, c) extends from below the bottom of the top plates in the lower storey to above the top of the bottom plate in the upper storey ,and d) completely fills the portion of the vertical space between the headers and between the wall plates. (See Note A-3.1.11.7.(8).) 9.10.16.4. Penetration of Fire Blocks 1) Where fire blocks are pierced by pipes, ducts or other elements, the effectiveness of the fire blocks shall be maintained around such elements. (See also Note A-3.1.11.7.(7).) 9.10.17. Flame-Spread Limits 9.10.17.1. Flame-Spread Rating of Interior Surfaces 1) Except as otherwise provided in this Subsection, the exposed surface of every interior wall and ceiling, including skylights and glazing, shall have a surface flame-spread rating of not more than 150. 2) Except as permitted in Sentence (3), doors need not conform to Sentence (1) provided they have a surface flame-spread rating of not more than 200. 3) Doors within dwelling units , other than garage doors, need not conform to Sentences (1) and (2). 9.10.17.2. Ceilings in Exits or Public Corridors 1) At least 90% of the exposed surface of every ceiling in an exit or ceiling that is not sprinklered in a public corridor shall have a surface flame-spread rating of not more than 25. (See Article 9.10.17.6.) 9.10.17.3. Walls in Exits 1) Except as provided in Sentence (2), at least 90% of the exposed surfaces of every wall in an exit shall have a surface flame-spread rating of not more than 25. (See Article 9.10.17.6.) 2) At least 75% of the wall surface of a lobby used as an exit in Article 9.9.8.5. shall have a surface flame-spread rating of not more than 25. (See Article 9.10.17.6.) 9.10.17.4. Exterior Exit Passageways 1) Where an exterior exit passageway provides the only means of egress from the rooms or suites it serves, the wall and ceiling finishes of that passageway, including the soffit beneath and the guard on the passageway, shall have a surface flame-spread rating of not more than 25, except that up to 10% of the total wall area and 10% of the total ceiling area is permitted to have a surface flame-spread rating of not more than 150. 9-76 Division B National Building Code of Canada 2025 Volume 2