Ontario Building Code Section 9.27: Guide to Cladding Attachment and Sealant Standards in London, Ontario
Sarah's Expert Insight
OBC Compliance Specialist
"In regions like London and Muskoka, where temperature swings and wind-driven rain are common, the choice of sealant (ASTM C920) is non-negotiable for preventing premature envelope failure. At empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure that cladding is never just 'nailed on,' but secured to the correct sheathing thickness or furring to meet both OBC safety standards and long-term aesthetic durability."
Understanding the Ontario Building Code (OBC) is essential for maintaining the structural integrity and weather resistance of any residential project. At empcontracting.ca Inc. your construction contractor in London, Ontario, we strictly adhere to these regulations to ensure high-quality exterior finishes.
9.27.4.2. Sealant Material Requirements
Sealants play a critical role in protecting the building envelope from moisture and air infiltration. According to the OBC, sealants used in cladding systems must meet the following criteria:
Core Material Properties
- Durability: Must be a non-hardening type suitable for exterior exposure.
- Weather Resistance: Selected specifically to resist degradation from UV and temperature fluctuations.
- Compatibility: Must adhere securely to the specific substrate (wood, metal, or masonry) to which they are applied.
Industry Standards (ASTM Compliance)
To ensure long-term performance, sealants and backer rods must conform to specific ASTM standards, including ASTM C834 (Latex), ASTM C920 (Elastomeric), ASTM C1184 (Silicone), and ASTM C1311 (Solvent Release). Backer rods must comply with ASTM C1330.
9.27.5. Attachment of Cladding
Properly securing cladding is vital for wind resistance and structural stability. The code outlines specific requirements for fastening cladding to the building frame.
9.27.5.1. General Attachment Rules
Generally, cladding must be fastened to framing members, furring, or blocking. However, exceptions exist for specific materials attached directly to sheathing:
- Lumber and Vinyl Siding: May be attached to sheathing if it is at least 14.3 mm lumber, 12.5 mm plywood, or 12.5 mm OSB.
- Metal Siding and Wood Shingles: May be attached to sheathing as thin as 7.5 mm for plywood or OSB, and 14.3 mm for lumber.
- ICF Construction: Cladding can be attached to the web fastening strips of flat wall insulating concrete forms using approved screws.
9.27.5.2 & 9.27.5.3. Blocking and Furring Specs
When additional support is required, the OBC specifies the following dimensions:
- Blocking: Minimum 38 mm by 38 mm lumber, spaced no more than 600 mm o.c.
- Furring: Minimum 19 mm by 38 mm lumber when applied over sheathing.
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.