2024 Ontario Building Code: Maximum Spans for Built-up Floor Beams (Table 9.23.4.2.-H)
Sarah's Expert Insight
OBC Compliance Specialist
"In high-end renovations across London and Oakville, we frequently see requests for open-concept layouts that push these span limits to their maximum. At empcontracting.ca Inc., your construction contractor in London, Ontario, we emphasize that while Table 9.23.4.2.-H provides the minimum legal standard, factors like the 0.8 multiplier for concrete toppings in modern radiant-heat floors are often overlooked by less experienced builders, leading to structural sagging if not calculated correctly."
Overview of OBC Table 9.23.4.2.-H for Residential Construction
The 2024 Building Code Compendium provides specific guidelines for the maximum allowable clear spans of built-up floor beams that support no more than one floor. This table is essential for ensuring the structural integrity of residential buildings in Ontario. When planning your project with empcontracting.ca Inc. your construction contractor in London, Ontario, adhering to these dimensions ensures long-term safety and compliance.
Wood Species and Structural Grades
The maximum span is determined by the species of lumber and its structural grade. The table covers two main categories:
- Spruce-Pine-Fir (SPF): Includes Spruce, Jack Pine, Lodgepole Pine, and Balsam/Alpine Fir.
- Northern Species: Includes Canadian species covered by NLGA Standard Grading Rules.
Grades are split between Select Structural and No. 1 and No. 2, with Select Structural offering higher load-bearing capacities and longer spans for the same beam dimensions.
Beam Sizing and Ply Configurations
Spans are provided for various built-up configurations, typically using 38 mm thick lumber in multiple plies:
- 38 x 184 mm: Available in 3, 4, and 5-ply configurations.
- 38 x 235 mm: Standard for medium-span residential applications.
- 38 x 286 mm: Used for maximum span requirements in larger open-concept designs.
Critical Technical Notes for Compliance
To remain compliant with the Ontario Building Code, contractors must account for the following variables:
- Supported Length: This is calculated as half the sum of the joist spans on both sides of the beam.
- Concrete Toppings: If the floor includes a concrete topping (up to 51 mm), the maximum span must be reduced by multiplying the table value by 0.8.
- Bearing Lengths: While standard beams require 76 mm of bearing, 3-ply beams with supported lengths exceeding 4.2 m require a minimum of 114 mm.
- Clear Spans: The table values refer to clear spans between supports; the total beam length must include the necessary bearing lengths at each end.
Disclaimer: This content is generated from the Ontario Building Code for educational purposes. Always consult with a licensed professional engineer or your local building department before starting any construction project in London, Ontario.