3.1.6.10 — Combustible Components in Exterior Walls

(1) Except as provided in Sentences (2) and (4), combustible components are permitted to be used for an exterior non-loadbearing wall assembly in a building required to be of noncombustible construction, provided that, (a) the building is, (i) not more than 3 storeys in building height, or (ii) not more than 6 storeys in building height if sprinklered, (b) when tested in accordance with CAN/ULC-S134, "Fire Test of Exterior Wall Assemblies", the wall assembly satisfies the following criteria for testing and conditions of acceptance: (i) flaming on or in the wall assembly does not spread more than 5 m above the opening, and (ii) the heat flux during the flame exposure on the wall assembly is not more than 35 kW/m2 measured at 3.5 m above the opening, and (c) the interior surfaces of the wall assembly are protected by a thermal barrier conforming to Sentence 3.1.5.12. (5). (2) Except as permitted by Articles 3.2.3.10. and 3.2.3.11., where the limiting distance in Tables 3.2.3.1.B. to 3.2.3.1.E. permits an area of unprotected openings of not more than 10% of the exposing building face, the construction requirements of Table 3.2.3.7. shall be met. (3) A wall assembly permitted by Sentence (1) that includes combustible cladding of fire-retardant treated wood shall be tested for fire exposure after the cladding has been subjected to an accelerated weathering test as specified in ASTM D2898, “Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing”. (4) The requirements of this Article do not apply where foamed plastic insulation is used in an exterior wall assembly of a building and the insulation is protected in conformance with Sentences 3.2.3.8. (1) and (2).

(1) Except as otherwise provided in this Subsection and Articles 3.2.2.16. and 3.2.3.19., a building or part of a building permitted to be of encapsulated mass timber construction is permitted to include structural mass timber elements, including beams, columns, arches and wall, floor and roof assemblies, provided they comply with Sentences (2) and (3). (2) Structural mass timber elements referred to in Sentence (1) shall, (a) except as provided in Sentence (4), be arranged in heavy solid masses containing no concealed spaces, (b) have essentially smooth flat surfaces with no thin sections or sharp projections, and (c) except as provided in Sentence 3.1.6.17. (1), conform to the minimum dimensions stated in Table 3.1.6.3. (3) Adhesives used in structural mass timber elements referred to in Sentence (1) that are constructed of cross-laminated timber shall conform to the elevated temperature performance requirements in ANSI/APA PRG 320, “Standard for Performance-Rated Cross-Laminated Timber”. (4) Concealed spaces are permitted within structural mass timber elements referred to in Sentence (2) and need not conform to Sentence 3.1.6.4. (1) provided the concealed spaces are, (a) sprinklered and divided into compartments by fire blocks in conformance with Subsection 3.1.11., (b) completely filled with rocks or slag fibre insulation conforming to CAN/ULC-S702.1 “Standard for Mineral Fibre Thermal Insulation for Buildings, Part 1: Material Specification” and having a density not less than 32 kg/m3, (c) if horizontal, lined with not less than a single layer of 12.7 mm thick Type X gypsum board or noncombustible material providing an encapsulation rating of not less than 25 min, or (d) if vertical, lined with not less than a single layer of 12.7 mm thick Type X gypsum board or noncombustible material providing an encapsulation rating of not less than 25 min and vertically divided into compartments by fire blocks in conformance with Subsection 3.1.11.

(1) Except as provided in Sentences (2), (3) and (6), cladding on an exterior wall assembly of a building or part of a building permitted to be of encapsulated mass timber construction shall be noncombustible. (2) Except as provided in Sentences (3) to (5), cladding on an exterior wall assembly of a building or part of a building permitted to be of encapsulated mass timber construction is permitted to consist of, (a) combustible cladding that, (i) is not contiguous over more than 4 storeys, (ii) represents not more than 10% of the cladding on each exterior wall of each storey, (iii) is not more than 1.2 m in width, (iv) has a flame-spread rating not more than 75 on any exposed surface, or any surface that would by exposed by cutting through the material in any direction, (v) is separated from other portions of combustible cladding on adjacent storeys by a horizontal distance of not less than 2.4 m, and (vi) is separated from other portions of combustible cladding by a horizontal distance of not less than 1.2 m, (b) combustible cladding that, (i) is not contiguous across adjacent storeys, (ii) represents not more than 10% of the cladding on each exterior wall of each storey, (iii) has a flame-spread rating not more than 75 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, and (iv) is separated from other portions of combustible cladding on adjacent storeys by a horizontal distance of not less than 2.4 m, (c) combustible cladding representing up to 100% of the cladding on exterior walls of the first storey, provided all portions of the cladding can be directly accessed and are located not more than 15 m from a street or access route conforming to Article 3.2.5.6., measured horizontally from the face of the building, (d) except as provided in Sentence (4), a wall assembly that satisfies the criteria described in Clause 3.1.5.5. (1)(b), or (e) a combination of noncombustible cladding and the cladding described in Clauses (a) to (d). (3) The permitted area of combustible cladding referred to in Clause (2)(a) or (b) shall not exceed 5% of the cladding on each exterior wall of each storey where firefighting facilities cannot reach the building within 10 min of the alarm being received. (4) An exterior wall assembly constructed in conformance with Section 6 of MMAH Supplementary Standard SB-2, “Fire Performance Ratings” is deemed to satisfy the criteria of Clause (2)(d). (5) Except as provided in Article 3.2.3.10., where the limiting distance in Table 3.2.3.1.D. or Table 3.2.3.1.E. permits an area of unprotected openings of not more than 10% of the exposing building face, the construction requirements of Table 3.2.3.7. shall be met. (6) A wall assembly conforming to Clause (2)(d) that includes combustible cladding made of fire-retardant-treated wood shall be tested for fire exposure after the cladding has been subjected to the accelerated weathering test specified in ASTM D2898, “Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing”. (7) Where combustible cladding conforming to Clause (2)(a) or (b) on an exterior wall of a fire compartment is exposed to combustible cladding conforming to Clause (2)(a) or (b) on an exterior wall of the same fire compartment or of another fire compartment, and the planes of the two walls are parallel or at an angle less than 135° measured from the exterior of the building, the different portions of combustible cladding shall, (a) be separated by a horizontal distance of not less than 3 m, and (b) not be contiguous over more than 2 storeys.