National baseline
The NBC defines the Part 3 / Part 9 boundary based on building area, height, and occupancy type, with specific crossover provisions.
Canadian building code question
What is the difference between Part 3 and Part 9 of the Canadian building code?
Part 9 covers small buildings — generally residential and small commercial structures up to 3 storeys and 600 m² in building area — while Part 3 covers all other buildings. The applicable part determines the entire compliance framework including structural, fire safety, accessibility, and means of egress requirements.
One of the most fundamental questions in Canadian building code compliance is whether a project falls under Part 3 or Part 9. The answer affects every aspect of the design because each part provides a complete but different set of requirements. Part 9 uses prescriptive, simplified rules for small buildings, while Part 3 provides more detailed, performance-oriented requirements for larger and more complex buildings.
What to check first
- Part 9 generally applies to buildings up to 3 storeys and 600 m² in building area with specific occupancy types.
- Part 3 applies to all buildings that do not qualify for Part 9 — larger, taller, or more complex occupancies.
- Some provisions in Part 3 apply to all buildings regardless of size, even those primarily governed by Part 9.
Jurisdiction notes
Provincial adoption
Provincial adoptions may adjust the Part 9 scope — confirm the applicable thresholds in your jurisdiction.
Project variables
Building area, number of storeys, occupancy classification, and whether the building is sprinklered can all affect which part applies.
Work through it in this order
- Determine building area, height, and occupancy classification.
- Check whether the building qualifies for Part 9 based on the applicable thresholds.
- If Part 9 applies, identify which Part 3 provisions still apply (e.g., fire protection, structural).
- Confirm the provincial adoption and any threshold adjustments.
Common questions
Can a building be governed by both Part 3 and Part 9?
Yes — Part 9 buildings must still comply with certain Part 3 provisions, and additions to Part 9 buildings can trigger Part 3 requirements.
What happens if a renovation pushes a Part 9 building past the size limit?
If the building exceeds Part 9 thresholds after renovation, the entire building or the addition may need to comply with Part 3 requirements.
Is Part 9 only for houses?
No — Part 9 covers all small buildings that meet the size and occupancy thresholds, including small commercial, office, and institutional buildings.