OBC 2024 Masonry Flashing & Weep Hole Requirements | empcontracting.ca Inc. London Ontario
Sarah's Expert Insight
OBC Compliance Specialist
"In the volatile climates of London, Oakville, and Muskoka, the freeze-thaw cycle can turn minor moisture trapped in a masonry cavity into a major structural failure. At empcontracting.ca Inc. your construction contractor in London, Ontario, we treat the 800mm weep hole spacing and the 150mm flashing upturn as critical benchmarks to ensure your building's exterior remains resilient against Ontario's heavy driving rains and snowmelt."
Understanding the 2024 Ontario Building Code (OBC) requirements for masonry moisture management is essential for long-term structural durability. At empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure every build adheres to the highest standards of throughwall flashing and weep hole installation.
9.20.13.4. Extension of Flashing and Moisture Control
Proper flashing extension is vital for directing water away from sensitive joints. When installing beneath masonry window sills or over lintels, the flashing must extend from the front edge of the masonry and tuck safely behind the sill. This prevents water ingress at the most vulnerable points of the building envelope.
Exceptions for Non-Jointed Copings
Per OBC 9.20.13.4.(2), flashing may be omitted only if the masonry sill or wall top is protected by an impervious, non-jointed masonry coping that meets the specific standards of Article 9.20.13.12.
9.20.13.5. & 9.20.13.6. Flashing for Weep Holes in Masonry Veneer
The 2024 Building Code Compendium specifies precise dimensions for flashing beneath weep holes to ensure effective drainage:
- Masonry Backing: Flashing must be bedded at least 25 mm into the inside wythe and extend 5 mm beyond the outer face.
- Wood Frame Construction: For masonry veneer over wood frames, the flashing must extend 150 mm up the wood-frame wall and be installed behind the sheathing membrane to ensure a watertight seal.
9.20.13.7. & 9.20.13.8. Required Weep Hole Spacing and Watertight Joints
Maximum Spacing Standards
To prevent moisture accumulation in the air space, weep holes must be provided at the bottom of cavities and above lintels. The OBC mandates a maximum spacing of 800 mm apart. This ensures that any water collecting in the cavity is redirected to the exterior immediately.
The Importance of Watertight Joints
All joints within the flashing itself must be made completely watertight. As a senior consultant for empcontracting.ca Inc. your construction contractor in London, Ontario, I emphasize that even a minor failure in flashing continuity can lead to significant efflorescence or structural decay over time.
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.