Canadian building code question

What are the building code requirements for exit capacity in Canada?

Exit capacity is determined by the occupant load of the floor area served and the width per person required by the code. The total exit width must accommodate the occupant load, with adjustments for stair capacity, door width minimums, and the loss of any single exit. Sprinklering can reduce the required width per person.

Exit capacity calculation is the link between occupant load and physical exit dimensions. The code requires enough total exit width to move the building's occupants out safely, accounting for the possibility that one exit may be blocked. Getting exit capacity wrong can lead to code deficiencies that require costly redesign of stairwells, corridors, or exit doors.

What to check first

  • Total exit width must accommodate the occupant load using a width-per-person factor specified by the code.
  • The capacity calculation must account for the loss of the largest single exit — the remaining exits must still handle the full occupant load in some code editions.
  • Stair width capacity uses a different width-per-person factor than door or corridor capacity.

Jurisdiction notes

National baseline

Start with the NBC provisions for exit width, width-per-person factors, and the requirements for exit capacity with one exit lost.

Province and edition check

Width-per-person factors and the exit loss calculation method may vary between code editions. Confirm the adopted edition.

Sprinkler reduction

Sprinklered buildings may qualify for a reduced width-per-person factor, which decreases the required total exit width.

Work through it in this order

  1. Calculate the occupant load for each floor area served by the exits.
  2. Determine the width-per-person factor for doors, corridors, and stairs under the applicable code edition.
  3. Calculate the total required exit width and distribute it among the available exits.
  4. Verify that the remaining exits can handle the occupant load with the largest single exit removed.

Common questions

How is exit width per person calculated?

The code specifies a width-per-person factor (in millimetres per person) that varies by exit component type (door, corridor, stair) and whether the building is sprinklered. Multiply the occupant load by this factor to get the required total width.

Does exit capacity change if the building is sprinklered?

In many code editions, sprinklered buildings qualify for a lower width-per-person factor, which reduces the total required exit width. Verify the specific provisions.

What happens when one exit is blocked?

The code requires that the remaining exits can still handle the occupant load. This typically governs the minimum number and distribution of exits.