Canadian building code question

What are the building code requirements for occupant load calculation in Canada?

Occupant load is calculated by dividing the floor area by the area-per-person factor specified in the NBC for each use type. Different uses have different factors, and the occupant load drives exit capacity, plumbing fixture count, ventilation, and fire alarm requirements.

Occupant load calculation is the starting point for many code requirements — exits, plumbing, ventilation, and fire protection all depend on it. The code provides area-per-person factors for each use type, and the calculation must be done for every distinct use area on each floor. Errors in occupant load cascade through the entire code compliance process.

What to check first

  • The NBC provides area-per-person factors for each occupancy use type in a table — use the factor that matches the actual intended use, not the occupancy classification alone.
  • Occupant load is calculated separately for each distinct use area and summed for the floor and building.
  • The calculated occupant load is a minimum — the actual occupant load may be higher if the space is configured for more people than the table suggests.

Jurisdiction notes

National baseline

Start with the NBC occupant load table that provides area-per-person factors by use type.

Province and edition check

Occupant load factors are generally consistent across provinces but confirm the adopted edition as some factors have been updated.

Downstream requirements

Occupant load feeds exit capacity, plumbing fixture count, ventilation rates, and fire alarm occupancy notification requirements.

Work through it in this order

  1. Identify each distinct use area on each floor and match it to the NBC occupant load table category.
  2. Calculate the floor area of each use area and divide by the applicable area-per-person factor.
  3. Sum the occupant loads for each floor and for the building to determine total occupant load.
  4. Apply the occupant load to downstream requirements: exits, plumbing, ventilation, and fire alarm.

Common questions

What area-per-person factor applies to an office?

The NBC occupant load table provides a specific factor for business use. The exact value depends on the code edition. Verify the cited provision.

Can the occupant load be lower than the calculated value?

Generally, no. The calculated value is the minimum. However, some code editions allow the authority having jurisdiction to accept a lower occupant load based on fixed seating or other limiting conditions.

How does mixed use affect occupant load?

Each use area within a mixed-use building is calculated separately using the factor for that use type. The occupant loads are then summed for exit capacity and other downstream requirements.