3.1.6.8.Combustible Window Sashes and Frames

(1) Combustible window sashes and frames are permitted in a building or part of a building permitted to be of encapsulated mass timber construction, provided (a) each window in an exterior wall face is an individual unit separated from every other opening in the wall by noncombustible wall construction or mass timber wall construction conforming to the dimensions stated in Table 3.1.6.3., (b) windows in exterior walls in contiguous storeys are separated by not less than 1 m of noncombustible wall construction or mass timber wall construction conforming to the dimensions stated in Table 3.1.6.3., and (c) the aggregate area of openings in an exterior wall face of a fire compartment is not more than 40% of the area of the wall face. r1 3.1.6.9. Exterior Cladding (1) Except as provided in Sentences (2) to (5) and (8), cladding on an exterior wall assembly of a building or part thereof permitted to be of encapsulated mass timber construction shall be (a) noncombustible, (b) a material or combination of materials that satisfy the criteria of Sentence 3.1.5.1.(2), (c) except as provided in Sentence (6), a wall assembly that satisfies the criteria of Clause 3.1.5.5.(1)(b), or (d) a combination of the cladding described in Clauses (a) to (c). (See Note A-3.1.6.9.(1), (2), (4) and (5)) (2) Except as provided in Sentences (3) to (5) and (7), cladding on an exterior wall assembly of a building or part thereof permitted to be of encapsulated mass timber construction that is not more than 12 storeys in building height 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, or (d) a combination of cladding described in Sentence (1) and the cladding described in Clauses (a) to (c). (See Note A-3.1.6.9.(1), (2), (4) and (5)) (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) Except as provided in Sentences (5) and (7), cladding on an exterior wall assembly of a building or part thereof permitted to be of encapsulated mass timber construction that is not more than 6 storeys in building height is permitted to consist of (a) combustible cladding that (i) represents not more than 10% of the cladding on each exterior wall of each storey, and (ii) 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, or (b) a combination of the cladding described in Clause (a) and the cladding described in Sentence (1) and Clause (2)(c). (See Note A-3.1.6.9.(1), (2), (4) and (5)) (5) Except as provided in Sentence (7), cladding on an exterior wall assembly of a building or part thereof permitted to be of encapsulated mass timber construction and not more than 4 storeys in building height is permitted to consist of combustible material with 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. (See Note A-3.1.6.9.(1), (2), (4) and (5).) (6) 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 (1)(c). (7) 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. (8) A wall assembly conforming to Clause (1)(c) 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, “Standard Practice for Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing,” (9) Where combustible cladding conforming to Clauses (2)(a), (b) or (4)(a) on an exterior wall of a fire compartment is exposed to combustible cladding conforming to Clause (2)(a), (b) or (4)(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.