OBC Cladding Guide: Shingle, Shake, and Plywood Standards for London, Ontario Construction
Sarah's Expert Insight
OBC Compliance Specialist
"Precision in joint staggering and lath projection is what separates a standard siding job from a high-performance building envelope. At empcontracting.ca Inc. your construction contractor in London, Ontario, we find that strictly following these exposure tables is especially critical in wind-prone areas like Oakville and the Muskoka lakes to prevent shingle curling and water penetration."
Adhering to the 2024 Ontario Building Code (OBC) is essential for ensuring the durability and weather resistance of any residential or commercial structure. As empcontracting.ca Inc. your construction contractor in London, Ontario, we specialize in high-precision cladding installations that meet and exceed these provincial standards.
9.27.7.4. Offsetting of Joints for Moisture Management
Proper joint placement is the first line of defense against water ingress. In single-course applications, joints must be offset by a minimum of 40 mm to ensure that joints in any two of three consecutive courses are staggered. For double-course applications, a 40 mm offset is required between the outer course and the under-course, as well as between succeeding courses.
9.27.7.5. Fastening to Lath and Substrates
When lath is utilized in double-course applications, it must be securely fastened to the framing and spaced according to exposure requirements. Key specifications include:
- Butt Placement: Under-course butts must rest on the top edge of the lath.
- Fastening: Outer course shingles must be secured with nails long enough to fully penetrate the lath.
- Projection: Shingle or shake butts must project at least 12 mm below the bottom edge of the lath to facilitate proper drainage.
9.27.7.6. Exposure and Thickness Requirements
The OBC dictates specific maximum exposure limits to prevent wind uplift and material degradation. For a standard 450 mm shingle, the maximum exposure is 216 mm for single coursing and 356 mm for double coursing, with a minimum butt thickness of 11 mm.
9.27.8. Plywood Material Standards
Plywood cladding must be exterior grade and conform to recognized standards such as CSA O121 (Douglas fir plywood) or CSA O151 (Canadian softwood plywood). Ensuring your materials meet these ANSI and CSA benchmarks is vital for long-term structural integrity in the variable Ontario climate.
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.