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OBC DIVISION B · PART 9 · SECTION 9.4 — STRUCTURAL REQUIREMENTS

When can you use Part 9 span tables instead of an engineer in Ontario?

You can use the prescriptive span tables when members, loads and spans fall within Part 9 limits for conventional wood-frame construction. Anything outside those limits, like long clear spans or heavy point loads, needs Part 4 engineering.

Code reference
Structural members within the scope of Part 9 may be sized using the applicable span tables and prescriptive provisions, provided loads and configurations fall within stated limits. Members or loading conditions outside those limits, or not addressed by Part 9, must be designed in accordance with Part 4 using accepted engineering practice.
OBC Division B, Subsection 9.4.1.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

Span tables cover typical joists, rafters, lintels, and beams under standard residential loads. You leave the tables when you have open-concept spans beyond tabulated values, concentrated loads such as a beam bearing mid-span on another beam, tall walls, unusual snow accumulation, or engineered products like LVL and I-joists, which follow manufacturer literature or engineering. Trusses always require engineered design. Mixing prescriptive and engineered elements is normal; just document who designed what so the plans examiner can trace responsibility.

Plain language

For a normal house frame, the code's ready-made tables tell you what size joists and beams to use, no engineer needed. Big open spans, unusual loads, or special products push you to a professional engineer's design.

Related questions

What design loads apply to houses under Part 9 in Ontario?What are the basic foundation design rules for houses in Ontario?

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.