Ontario Building Code 2024: Fire-Resistance and Storey Limits for Group C Residential Buildings
Sarah's Expert Insight
OBC Compliance Specialist
"Navigating the fire-resistance ratings for multi-storey Group C buildings is critical for ensuring both safety and cost-efficiency in London's growing mid-rise market. At empcontracting.ca Inc., we emphasize early integration of these 1-hour fire separation requirements to streamline the permitting process for our clients in London, Oakville, and Muskoka."
Understanding the complexities of the 2024 Ontario Building Code (OBC) is essential for successful multi-residential developments. Whether you are planning a mid-rise project or a smaller residential complex, empcontracting.ca Inc. your construction contractor in London, Ontario, provides the expertise needed to navigate these technical requirements.
OBC 3.2.2.51: Multi-Storey Construction Requirements (4 to 6 Storeys)
This section of the OBC Compendium defines the maximum building area and fire-resistance standards for mid-rise residential structures. Key regulations include:
- Area Limits: Maximum allowable area per floor decreases as height increases, ranging from 2,250 m² for 4 storeys down to 1,500 m² for 6 storeys.
- Fire-Resistance Ratings (FRR): Floor assemblies, roof assemblies, and mezzanines must generally maintain a minimum 1-hour fire-resistance rating.
- Material Standards: While combustible construction is permitted, roofs exceeding 25m in height from the first storey must utilize noncombustible materials or fire-retardant-treated wood.
Mixed-Use Occupancy Integration
Provisions are made for Group A, Division 2 and Group E major occupancies to be located within these buildings, provided they are situated below the third storey. Storage garages are permitted below the fourth storey, ensuring a safe separation of uses in urban residential developments.
OBC 3.2.2.52: Sprinklered Group C Buildings up to 4 Storeys
For residential buildings (excluding retirement homes) that are sprinklered throughout, this section provides specific area thresholds and safety mandates:
- Building Area: Limits are strictly enforced based on height, allowing up to 7,200 m² for a single storey, scaling down to 1,800 m² for 4 storeys.
- Loadbearing Support: Loadbearing walls, columns, and arches must possess a fire-resistance rating equivalent to the assembly they support to ensure structural integrity during an incident.
- Internal Exceptions: In specific cases where no dwelling unit is situated above another, the fire-resistance rating for floor assemblies within the unit may be waived, offering design flexibility for townhome-style builds.
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.