Canadian building code question

What are the building code requirements for fourplex buildings in Canada?

Fourplex buildings in Canada typically fall under Part 9 of the National Building Code if they are three storeys or less and within the building area limits. Fire separation between dwelling units, egress from each unit, and minimum spatial requirements are key compliance areas.

Fourplexes are increasingly popular as municipalities across Canada encourage gentle density. Understanding whether a fourplex falls under Part 9 or Part 3 of the NBC, and how fire separation, egress, and accessibility requirements apply, is essential for designers and builders entering this growing market.

What to check first

  • Most fourplexes fall under Part 9 of the NBC if they are three storeys or less and within area limits — otherwise Part 3 applies.
  • Fire separations between dwelling units must meet minimum fire-resistance ratings as specified in the applicable Part.
  • Each dwelling unit must have independent egress that meets code requirements for exit access and travel distance.

Jurisdiction notes

NBC baseline

The National Building Code sets minimum requirements for residential buildings containing four or fewer dwelling units under Part 9, provided height and area thresholds are met.

Provincial variations

Each province adopts the NBC with possible amendments. Ontario, BC, Alberta, and Quebec may have specific requirements for multi-unit residential buildings that affect fourplex design.

Municipal zoning

Even where the building code permits a fourplex, municipal zoning must allow four dwelling units on the lot. Many municipalities are currently updating zoning to permit more gentle density.

Work through it in this order

  1. Confirm the fourplex meets Part 9 thresholds for height, area, and occupancy — otherwise Part 3 applies.
  2. Verify zoning permits four dwelling units on the subject lot.
  3. Design fire separations between all dwelling units to meet the required fire-resistance rating.
  4. Ensure each unit has independent, code-compliant egress including exit access and exterior paths.
  5. Address sound transmission, accessibility, and energy code requirements as applicable.

Common questions

Does a fourplex fall under Part 9 or Part 3 of the building code?

Most fourplexes fall under Part 9 if they are three storeys or less and within the building area limits. If these thresholds are exceeded, Part 3 applies with more complex requirements.

What fire separation is required between fourplex units?

The required fire-resistance rating depends on whether the building falls under Part 9 or Part 3 and the specific construction type. Consult the applicable NBC section for the exact rating.

Are fourplexes eligible for Part 9 energy code compliance?

Part 9 energy requirements apply to buildings within Part 9 scope. The specific compliance path depends on the province and the applicable energy code version.