Ontario Building Code Roofing Standards: Sheet Metal, Selvage, and Rubberized Asphalt Guide
Sarah's Expert Insight
OBC Compliance Specialist
"These specific OBC sections regarding membrane overlaps and metal thickness are vital for the extreme weather transitions we see in London, Oakville, and Muskoka. As empcontracting.ca Inc. your construction contractor in London, Ontario, I emphasize the double-coverage and drip-edge requirements to our clients because they are the primary defense against ice damming and moisture penetration during Ontario's harsh winters."
Navigating the complexities of the 2024 Building Code Compendium is essential for any successful build. At empcontracting.ca Inc. your construction contractor in London, Ontario, we specialize in implementing these high-level roofing standards to ensure long-term durability and compliance.
Roof Edge and Gravel Stop Requirements (9.26.11.10)
Proper drainage at the roof edge is critical for preventing water ingress. Under Section 9.26.11.10, cant strips may be omitted if a gravel stop is installed. However, the roofing membranes must be carried over the edge before the gravel stop is fastened, with two plies of membrane mopped to the surface before the final flood coat. This creates a seamless, watertight seal.
Drip Edge Functionality
Gravel stops must extend over the roof edge to form a drip or be flashed appropriately to ensure water is shed away from the building structure.
Selvage and Sheet Metal Roofing Standards (9.26.12 & 9.26.13)
For wide selvage asphalt roofing, the code mandates double coverage across the entire roof surface, with all plies cemented together to guarantee watertight joints.
Sheet Metal Thickness and Support
When installing sheet metal roofing, material thickness is strictly regulated to ensure structural integrity:
- Galvanized Steel: Minimum 0.33 mm
- Copper or Zinc: Minimum 0.46 mm
- Aluminum: Minimum 0.48 mm
If the metal roofing is not supported by full decking, the panels must be specifically designed to handle Ontario's specified live loads, particularly snow accumulation.
Specialized Materials: Polyester and Rubberized Asphalt
Glass Reinforced Polyester (9.26.14)
Similar to metal roofing, if glass reinforced polyester panels span between spaced supports, they must be engineered to support all specified roof loads.
Hot Applied Rubberized Asphalt (9.26.15)
Installation of hot applied rubberized asphalt must strictly adhere to CAN/CGSB-37.51-M, ensuring the waterproofing layer is applied correctly for high-performance protection.
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.