OBC 2024 Guide: Snow Load Standards for Gable and Arch Roofs in London, Ontario
Sarah's Expert Insight
OBC Compliance Specialist
"In regions like London and Muskoka, the interaction between roof slope and wind exposure creates significant unbalanced snow loads that can compromise structural trusses if not calculated correctly. As empcontracting.ca Inc. your construction contractor in London, Ontario, we meticulously apply these 2024 standards to ensure your build withstands the heavy, shifting snowpacks typical of our Ontario winters."
Understanding the 2024 Ontario Building Code (OBC) is essential for any structural project. As empcontracting.ca Inc. your construction contractor in London, Ontario, we prioritize compliance with Section 4.1.6.9 and 4.1.6.10 regarding snow accumulation on specialized roof shapes.
4.1.6.9. Snow Load Requirements for Gable Roofs
The OBC specifies that for all gable roofs, full and partial load cases must be analyzed. When the roof slope exceeds 15°, contractors must account for unbalanced load cases to ensure the structural integrity of the building under heavy snowfall.
Unbalanced Load Calculations
For roofs with a slope of α > 15°, the accumulation factor (Ca) is calculated as follows:
- Upwind Side: The accumulation factor is taken as 0.
- Downwind Side: For slopes between 15° and 20°, Ca is 0.25 + α/20. For slopes between 20° and 90°, Ca is set at 1.25.
Additionally, the wind exposure factor (Cw) is typically set to 1.0 for the unbalanced load case to simulate worst-case accumulation scenarios.
4.1.6.10. Arch Roofs, Curved Roofs, and Domes
For non-linear roof structures like domes and arches, the code demands rigorous assessment of rise-to-span ratios. If the ratio (h/b) exceeds 0.05, specific unbalanced load cases defined in the compendium must be applied to ensure safety and prevent localized structural failure.
Full and Partial Load Considerations
Every curved or arched structure must be evaluated for both full and partial loading, as specified in Article 4.1.6.3., to account for the unique way snow accumulates and slides on non-planar surfaces.
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.