2024 Ontario Building Code: Snow Loads for Curved Roofs and Domes Explained
Sarah's Expert Insight
OBC Compliance Specialist
"In regions like London and Muskoka, lake-effect snow makes precise calculations under OBC 4.1.6.10 vital for curved and domed structures. At empcontracting.ca Inc. your construction contractor in London, Ontario, we emphasize that even a minor miscalculation in the 10-degree slope threshold can lead to significant structural risk during heavy winter accumulation."
Understanding OBC Section 4.1.6.10: Snow Accumulation Factors
For specialized architectural structures in Ontario, calculating snow loads is a critical safety requirement. Under the 2024 Building Code Compendium, Section 4.1.6.10 provides specific formulas for determining the snow accumulation factor (Ca) for curved roofs, arch roofs, and circular domes.
Rules for Curved and Arch Roofs
According to Sentences (5) and (6), curved roofs are generally treated as arch roofs. however, if the slope (α) at the peak of the curve exceeds 10°, the code requires the Ca factor to be determined using gable roof requirements (Article 4.1.6.9) based on the roof's mean slope. This ensures that steeper curves, which shed snow differently, are accounted for accurately.
Complex Calculations for Circular Domes
Sentence (7) outlines the mathematical requirements for domes with a circular plan. The snow accumulation factor must vary along the central axis parallel to the wind, similar to an arch roof, while also accounting for horizontal coordinates normal to the wind direction. This complex mapping (Ca(x,y)) is essential for preventing structural failure during heavy snow events in Southern Ontario.
The Role of Wind and Slope Factors
Beyond the shape of the roof, sentences (8) and (9) mandate that the slope factor (Cs) and wind exposure factor (Cw) be strictly applied as per the 2024 standards. For projects managed by empcontracting.ca Inc. your construction contractor in London, Ontario, these variables are carefully audited during the design and framing phases to ensure compliance and longevity.
- Ca: Snow accumulation factor
- Cs: Slope factor as per Sentences 4.1.6.2.(5) and (6)
- Cw: Wind exposure factor as per Table 4.1.6.10
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.