The Ontario Building Code | Spans for Joists, Rafters and Beams
9.23.4.2. Spans for joists, Rafters and Beams
(1) Except as required in Sentence (2) and Article 9.23.13.10., the spans for wood joists and rafters shall conform to the spans shown in Tables A-1 to A-7 for the uniform live loads shown in the Tables.
(2) Spans for floor joists that are not selected from Tables A-1 and A-2 and that are required to be designed for the same loading conditions, shall not exceed the design requirements for uniform loading and vibration criteria.
(3) Spans for built-up wood and glued-laminated timber floor beams shall conform to the spans in Tables A-8 to A-11.
(4) Spans for roof ridge beams shall conform to the spans in Table A-12 for the uniform snow load shown.
In Plain Language
Spans for joists, rafters, and beams must not exceed the values set out in the referenced span tables, ensuring these members can safely carry their design loads over the distance between supports.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.