3.1.4.

(1) A building permitted to be of combustible construction is permitted to be constructed of combustible materials, with or without noncombustible components.

(1) Foamed plastics that form part of a wall or ceiling assembly in combustible construction shall be protected from adjacent spaces in the building, other than adjacent concealed spaces within attic or roof spaces, crawl spaces, and wall assemblies,

(a) by one of the interior finishes described in Subsections 9.29.4. to 9.29.9.,

(b) by any thermal barrier that meets the requirements of Sentence 3.1.5.12.(2)v1v2, or

(c) where the building does not contain a Group B or Group C major occupancy, by sheet metal,

(i) mechanically fastened to the supporting assembly independent of the insulation,

(ii) not less than 0.38 mm thick, and

(iii) with a melting point not below 650°C.

(2) The flame-spread rating on any exposed surface of combustible insulation, or any surface that would be exposed by cutting through it in any direction, shall be not more than 500.

(1) Optical fibre cables and electrical wires and cables installed in a building permitted to be of combustible construction shall,

(a) not convey flame or continue to burn for more than 1 min when tested in conformance with the Vertical Flame Test in Clause 4.11.1. of CAN/CSA-C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables”, or

(b) be located in,

(i) totally enclosed noncombustible raceways,

(ii) concealed spaces in walls,

(iii) concrete slabs, or

(iv) totally enclosed nonmetallic raceways conforming to Article 3.1.5.20.v1

(2) The requirement in Clause (1)(a) is considered to be met where the wires and cables,

(a) exhibit a vertical char of not more than 1.5 m when tested in conformance with the Vertical Flame Test – Cables in Cabletrough in Clause 4.11.4. of CSA C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables” (FT4 Rating), or

(b) exhibit a flame-spread of not more than 1.5 m, a smoke density of not more than 0.5 at peak optical density and a smoke density not more than 0.15 at average optical density when tested in conformance with the Flame and Smoke Test in the Appendix to CSA C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables” (FT6 Rating).

(3) Service-entrance cables for communication and community antennae distribution systems need not conform to Sentence (1) provided,

(a) the service-entrance cables are located in a building permitted to be of combustible construction and are not more than 3 m in length from the point of entry into the building or from the point of leaving protection as required in Clause (1)(b), or

(b) the service entrance cables enter into an electrical or telephone service room separated from the remainder of the building by a fire separation having a fire-resistance rating not less than 1 h.

(1) If fire-retardant treated wood is specified in this Part, the wood shall,

(a) be pressure impregnated with fire-retardant chemicals in conformance with CAN/CSA-O80 Series-M, “Wood Preservation”, and

(b) have a flame-spread rating not more than 25.

(1) If combustible construction is permitted and is not required to have a fire-resistance rating more than 45 min, heavy timber construction is permitted to be used.

(2) If heavy timber construction is permitted, it shall conform to Article 3.1.4.6.

(1) Wood elements in heavy timber construction shall be arranged in heavy solid masses and with essentially smooth flat surfaces to avoid thin sections and sharp projections.

(2) Except as permitted by Sentences (3) to (6) and (12), the minimum dimensions of wood elements in heavy timber construction shall conform to Table 3.1.4.6.

(3) Where splice plates are used at splices of roof arches supported on the tops of walls or abutments, roof trusses, roof beams and roof girders in heavy timber construction shall be not less than 64 mm thick.

(4) Floors in heavy timber construction shall be of glued-laminated or solid sawn plank not less than,

(a) 64 mm thick, splined or tongued and grooved, or

(b) 38 mm wide and 89 mm deep set on edge and well-spiked together.

(5) Floors in heavy timber construction shall be laid,

(a) so that no continuous line of end joints will occur except at points of support, and covered with,

(i) tongued and grooved flooring not less than 19 mm thick laid cross-wise or diagonally, or

(ii) tongued and grooved phenolic-bonded plywood, strandboard or waferboard not less than 12.5 mm thick, and

(b) not closer than 15 mm to the walls to provide for expansion, with the gap covered at the top or bottom.

(6) Roofs in heavy timber construction shall be of tongued and grooved phenolic-bonded plywood not less than 28 mm thick, or glued-laminated or solid sawn plank that is,

(a) not less than 38 mm thick, splined or tongued and grooved, or

(b) not less than 38 mm wide and 64 mm deep set on edge and laid so that no continuous line of end joints will occur except at the points of support.

(7) Wood columns in heavy timber construction shall be continuous or superimposed throughout all storeys.

(8) Superimposed wood columns in heavy timber construction shall be connected by,

(a) reinforced concrete or metal caps with brackets,

(b) steel or iron caps with pintles and base plates, or

(c) timber splice plates fastened to the columns by metal connectors housed within the contact faces.

(9) Where beams and girders in heavy timber construction enter masonry, wall plates, boxes of the self-releasing type or hangers shall be used.

(10) Wood girders and beams in heavy timber construction shall be closely fitted to columns, and adjoining ends shall be connected by ties or caps to transfer horizontal loads across the joints.

(11) In heavy timber construction, intermediate wood beams used to support a floor shall be supported on top of the girders or on metal hangers into which the ends of the beams are closely fitted.

(12) Roof arches supported on the tops of walls or abutments, roof trusses, roof beams and roof girders in heavy timber construction are permitted to be not less than 64 mm wide provided,

(a) where two or more spaced members are used, the intervening spaces are,

(i) blocked solidly throughout, or

(ii) tightly closed by a continuous wood cover plate not less than 38 mm thick secured to the underside of the members, or

(b) the space below the roof deck or sheathing is sprinklered.