The Ontario Building Code | Wood Roof Trusses

9.23.13.11. wood Roof Trusses

(1) Roof trusses that are not designed in accordance with Part 4 shall,

(a) 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

(b) not exceed the deflections shown in Table 9.23.13.11. when loaded with the ceiling load plus one and one-third times the specified roof snow load for 1 h.

Table 9.23.13.11.
Maximum Roof Truss Deflections

Forming Part of Sentence 9.23.13.11.(1)

Item

Column 1

Truss Span

Column 2

Type of ceiling

Column 3

Maximum Deflection

1.

4.3 m or less

plaster or gypsum board

1/360 of the span

Other than plaster or gypsum board

1/180 of the span

2.

Over 4.3 m

plaster or gypsum board

1/360 of the span

Other than plaster or gypsum board

1/240 of the span

(2) The joint connections used in trusses described in Sentence (1) shall be designed in conformance with the requirements in Subsection 4.3.1.

(3) 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.

(4) 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.

(5) 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 Trusses for houses and Small buildings".

(6) 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 described in TPIC, "Truss design Procedures and Specifications for light Metal Plate Connected wood Trusses (Limit States design)".

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