OBC Fire Safety Regulations: Exposing Building Faces and Limiting Distances in Ontario
Sarah's Expert Insight
OBC Compliance Specialist
"In high-density residential areas of London and Oakville, managing limiting distances is often the most challenging aspect of site planning. At empcontracting.ca Inc. your construction contractor in London, Ontario, we emphasize the correct selection of soffit materials and fire-rated closures to ensure your project meets the 2024 Building Code Compendium while maximizing your buildable footprint."
Understanding Fire Compartments and Exposing Building Faces (OBC 3.2.3.2)
Under the 2024 Ontario Building Code, the calculation of an exposing building face is critical for fire safety. When a building is divided by fire separations with a fire-resistance rating of at least 45 minutes, the area of the exposing building face can be calculated for each individual fire compartment. For buildings that are fully sprinklered and feature interconnected floor spaces, each storey can be considered a separate compartment, even with openings through floor assemblies.
Attic and Roof Space Enclosures
Per OBC 3.2.3.3, any exterior wall that encloses an attic or roof space located above an exposing building face must be constructed to the same safety standards as the face itself to ensure uniform fire protection across the building envelope.
Regulations for Walls with Minimal Limiting Distance (OBC 3.2.3.5)
When the limiting distance of a wall is less than 1.2 meters, specific protection measures for openings are required. Closures in these walls must have fire-protection ratings that align with the required fire-resistance rating of the wall. It is important to note that wired glass or glass blocks are strictly prohibited for use as closures in these high-risk scenarios.
Combustible Projections and Soffit Protection (OBC 3.2.3.6)
Combustible projections, such as balconies, canopies, and stairs, are heavily regulated to prevent fire spread between adjacent buildings. For most multi-unit buildings, these projections are not permitted within 1.2 meters of a property line or 2.4 meters of another combustible projection on the same property.
Soffit Material and Construction Requirements
Where the limiting distance is between 0.45 m and 1.2 m, roof soffits must meet specific material requirements to resist fire. Approved materials include:
- 0.38 mm thick sheet steel
- Unvented aluminum (CAN/CGSB-93.2-M)
- 12.7 mm thick gypsum board
- 11 mm thick plywood or 12.5 mm thick OSB
- 11 mm thick lumber
For combustible construction, these protective materials may be finished with either combustible or noncombustible materials, provided the underlying protection meets the code.
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.