OBC Roofing Standards: Flashing and Eave Protection for London Construction Projects
Sarah's Expert Insight
OBC Compliance Specialist
"In the heavy snow-load regions of London and Muskoka, strictly adhering to the 900 mm eave protection rule is critical for preventing ice damming and subsequent interior water damage. As empcontracting.ca Inc. your construction contractor in London, Ontario, we find that properly executed chimney saddles and masonry counter-flashing are the most effective ways to protect Southwestern Ontario homes from our intense freeze-thaw cycles."
Mastering Roofing Intersections Under the Ontario Building Code
Proper flashing and intersection management are vital for the structural integrity of any building. According to OBC 9.26.4.6, when built-up roofs meet masonry walls or chimneys, a cant strip must be utilized at the intersection. The roofing membrane must be mopped over this strip and extend at least 150 mm up the wall, ensuring a watertight seal that prevents moisture ingress at critical junctions.
Detailed Flashing Requirements for Masonry and Non-Masonry Walls
For masonry intersections, counter flashing must be embedded at least 25 mm into the masonry and lap the membrane by no less than 100 mm. For non-masonry walls, OBC 9.26.4.7 requires flashing plies to extend 150 mm up the wall behind the sheathing paper. This maintains the building envelope's integrity against wind-driven rain and snowmelt.
Chimney Saddles and Slope Protection
OBC 9.26.4.8 mandates the installation of chimney saddles for chimneys wider than 750 mm on sloping roofs. These saddles must be covered with sheet metal or equivalent roofing material and must be properly flashed and counterflashed to effectively redirect water flow around the chimney structure.
Understanding Eave Protection Requirements (OBC 9.26.5.1)
Eave protection is a mandatory requirement for most shingle, shake, or tile roofs in Ontario to prevent damage from ice damming. The protection must extend from the roof edge at least 900 mm up the slope, reaching at least 300 mm past the inner face of the exterior wall.
Exemptions to Eave Protection Rules
While eave protection is standard for heated dwellings, OBC 9.26.5.1.(2) provides specific exceptions. These include unheated garages, carports, and porches, as well as roofs with very steep slopes (1 in 1.5 or greater) or overhangs exceeding 900 mm. For expert implementation of these standards, consult with empcontracting.ca Inc. your construction contractor in London, Ontario.
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.