2025 National Building Code Guide: Minimum Exit Widths and Capacity for Ontario Construction
Sarah's Expert Insight
Senior Consultant at empcontracting.ca Inc.
"In London, Ontario, navigating the nuances of exit capacity is vital for passing municipal inspections and ensuring occupant safety in high-density areas. At empcontracting.ca Inc., we integrate these NBC 2025 width requirements into the initial framing and layout phases to prevent expensive structural modifications during the final stages of your build."
Understanding NBC 2025 Exit Width and Capacity Requirements
As the 2025 National Building Code (NBC) evolves, maintaining compliance regarding means of egress is critical for any development. Exit capacity is a fundamental safety metric that ensures all occupants can safely evacuate a building during an emergency. Determining these widths requires a precise calculation based on the building's occupant load and occupancy classification.
Calculating Occupant Load and Exit Width
Under the NBC 2025, the required width of an exit is generally determined by multiplying the number of persons intended to use the exit by a capacity factor. For most standard occupancies, these factors are:
- Stairs: 8 mm per person.
- Ramps and Doorways: 6.1 mm per person.
When you partner with empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure that your architectural plans account for these variables before the first shovel hits the ground.
Absolute Minimum Width Requirements
Regardless of the occupant load calculation, the NBC 2025 mandates absolute minimum widths to facilitate movement and accessibility:
- Public Corridors: Generally 1100 mm to allow for two-way traffic and mobility device clearance.
- Exit Stairs: Usually 1100 mm in commercial settings, though specific residential suites may allow for 900 mm.
- Doorways: Must provide a clear width of at least 800 mm to 850 mm, ensuring that hardware and door swings do not obstruct the required egress path.
Compliance in High-Density and Care Occupancies
Buildings classified under Group A (Assembly) or Group B (Care/Treatment) face more rigorous standards. In these environments, exit widths are often increased to accommodate medical equipment or higher volumes of people. Proper signage, lighting, and the absence of obstructions are equally vital to maintaining the integrity of the exit capacity.