3.1.4.7.Heavy Timber Construction

(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 3.1.4.7. (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, they 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. Table 3.1.4.7. Heavy Timber Dimensions Forming Part of Sentence 3.1.4.7.(2) Solid Sawn Glued-Laminated Round Supported Assembly Structural Element (width × depth), (width × depth), (diam), mm mm × mm mm × mm Columns 140 × 191 130 × 190 180 Arches supported on the tops of walls 89 × 140 80 × 152 --- or abutments Roofs only Beams, girders and trusses 89 × 140 80 × 152 --- Arches supported at or near the floor 140 × 140 130 × 152 --- line Columns 191 × 191 175 × 190 200 Floors, floors plus roofs 140 × 241 or 130 × 228 or Beams, girders, trusses and arches --- 191 × 191 175 × 190 (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 crosswise 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, strandboard or waferboard 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 underneath of the roof deck or sheathing is sprinklered.