| 9.23.14. |
Roof and Ceiling Framing |
| 9.23.14.1. |
Continuity of Rafters and Joists
- Roof rafters and joists and ceiling joists shall be continuous or shall be spliced over vertical supports that extend to suitable bearing.
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| 9.23.14.2. |
Framing around Openings
- Roof and ceiling framing members shall be doubled on each side of openings greater than 2 rafter or joist spacings wide.
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| 9.23.14.3. |
End Bearing Length
- The length of end bearing of joists and rafters shall be not less than 38 mm.
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| 9.23.14.4. |
Location and Attachment of Rafters
- Rafters shall be located directly opposite each other and tied together at the peak, or may be offset by their own thickness if nailed to a ridge board not less than 17.5 mm thick.
- Except as permitted in Sentence (3), framing members shall be connected by gusset plates or nailing at the peak in conformance with Table 9.23.3.4.
- Where the roof framing on opposite sides of the peak is assembled separately, such as in the case of factory-built houses, the roof framing on opposite sides is permitted to be fastened together with galvanized-steel strips not less than 200 mm by 75 mm by 0.41 mm thick spaced not more than 1.2 m apart and nailed at each end to the framing by at least two 63 mm nails.
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| 9.23.14.5. |
Shaping of Rafters
- Rafters shall be shaped at supports to provide even bearing surfaces and supported directly above the exterior walls.
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| 9.23.14.6. |
Hip and Valley Rafters
- Hip and valley rafters shall be not less than 50 mm greater in depth than the common rafters and not less than 38 mm thick, actual dimension.
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| 9.23.14.7. |
Intermediate Support for Rafters and Joists
- Ceiling joists and collar ties of not less than 38 mm by 89 mm lumber are permitted to be assumed to provide intermediate support to reduce the span for rafters and joists where the roof slope is 1 in 3 or greater.
- Collar ties referred to in Sentence (1) more than 2.4 m long shall be laterally supported near their centres by not less than 19 mm by 89 mm continuous members at right angles to the collar ties.
- Dwarf walls and struts are permitted to be used to provide intermediate support to reduce the span for rafters and joists.
- When struts are used to provide intermediate support they shall be not less than 38 mm by 89 mm material extending from each rafter to a loadbearing wall at an angle of not less than 45° to the horizontal.
- When dwarf walls are used for rafter support, they shall be framed in the same manner as loadbearing walls and securely fastened top and bottom to the roof and ceiling framing to prevent over-all movement.
- Solid blocking shall be installed between floor joists beneath dwarf walls referred to in Sentence (5) that enclose finished rooms.
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| 9.23.14.8. |
Ridge Support
- Except as provided in Sentence (4), roof rafters and joists shall be supported at the ridge of the roof by
- a loadbearing wall extending from the ridge to suitable bearing, or
- a ridge beam supported by not less than 89 mm length of bearing.
- Except as provided in Sentence (3), the ridge beam referred to in Sentence (1) shall conform to the sizes and spans shown in Span Table 9.23.4.2.-L, provided
- the supported rafter or joist length does not exceed 4.9 m, and
- the roof does not support any concentrated loads.
- The ridge beam referred to in Sentence (1) need not comply with Sentence (2) where
- the beam is of not less than 38 mm by 140 mm material, and
- the beam is supported at intervals not exceeding 1.2 m by not less than 38 mm by 89 mm members extending vertically from the ridge to suitable bearing.
- When the roof slope is 1 in 3 or more, ridge support need not be provided when the lower ends of the rafters are adequately tied to prevent outward movement.
- Ties required in Sentence (4) are permitted to consist of tie rods or ceiling joists forming a continuous tie for opposing rafters and nailed in accordance with Table 9.23.14.8.
Table 9.23.14.8.
Rafter-to-Joist Nailing (Unsupported Ridge)
Forming Part of Sentences 9.23.14.8.(5) and (6)
- Ceiling joists referred to in Sentence (5) shall be fastened together with at least one more nail per joist splice than required for the rafter to joist connection shown in Table 9.23.14.8.
- Members referred to in Sentence (6) are permitted to be fastened together either directly or through a gusset plate.
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| 9.23.14.9. |
Restraint of Joist Bottoms
- Roof joists supporting a finished ceiling, other than plywood, OSB or waferboard, shall be restrained from twisting along the bottom edges by means of furring, blocking, cross bridging or strapping conforming to Article 9.23.9.3.
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| 9.23.14.10. |
Ceiling Joists Supporting Roof Load
- Except as permitted in Sentence (2), ceiling joists supporting part of the roof load from the rafters shall be not less than 25 mm greater in depth than required for ceiling joists not supporting part of the roof load.
- When the roof slope is 1 in 4 or less, the ceiling joist sizes referred to in Sentence (1) shall be determined from Span Tables 9.23.4.2.-C to 9.23.4.2.-F and 9.23.4.2.-L for roof joists.
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| 9.23.14.11. |
Roof Trusses
- Roof trusses which are not designed in accordance with Part 4 shall
- be capable of supporting a total ceiling load (dead load plus live load ) of 0.35 kPa plus two and two-thirds times the specified live roof load for 24 h, and
- not exceed the deflections shown in Table 9.23.14.11. when loaded with the ceiling load plus one and one-third times the specified roof snow load for 1 h.
Table 9.23.14.11.
Maximum Roof Truss Deflections
Forming Part of Sentence 9.23.14.11.(1)
- The joint connections used in trusses described in Sentence (1) shall be designed in conformance with the requirements in Subsection 4.3.1. (See Note A-9.23.14.11.(2).)
- Where the length of compression web members in roof trusses described in Sentence (1) exceeds 1.83 m, such web members shall be provided with continuous bracing to prevent buckling.
- Bracing required in Sentence (3) shall consist of not less than 19 mm by 89 mm lumber nailed at right angles to the web members near their centres with at least two 63 mm nails for each member.
- Where the ability of a truss design to satisfy the requirements of Sentence (1) is demonstrated by testing, it shall consist of a full scale load test carried out in conformance with CSA S307-M, "Load Test Procedure for Wood Roof Trusses for Houses and Small Buildings."
- Where the ability of a truss design to satisfy the requirements of Sentence (1) is demonstrated by analysis, it shall be carried out in accordance with good engineering practice such as that described in TPIC 2014, "Truss Design Procedures and Specifications for Light Metal Plate Connected Wood Trusses (Limit States Design)."
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