Canadian building code question

What are the building code requirements for combustible and noncombustible construction in Canada?

The NBC classifies construction as combustible or noncombustible based on the materials used. Noncombustible construction is required for certain building heights, areas, and occupancies. Specific exceptions allow limited combustible materials within otherwise noncombustible buildings, subject to conditions.

The combustible vs noncombustible distinction is one of the most fundamental building code classifications because it determines allowable building height, building area, and construction type. The code defines noncombustible materials based on testing standards and then limits where combustible materials can be used based on fire safety risk. Understanding the exceptions is as important as understanding the rule.

What to check first

  • Noncombustible construction is required when building height, area, or occupancy exceeds the limits for combustible construction.
  • The code defines noncombustible materials based on CAN/ULC test standards — it is a performance classification, not a material list.
  • Specific exceptions permit combustible components (insulation, vapour barriers, interior finishes, etc.) within noncombustible buildings under defined conditions.

Jurisdiction notes

National baseline

Start with NBC Part 3 for building height and area limits by construction type, and the definition of noncombustible construction and noncombustible material.

Province and edition check

Mass timber provisions in recent code editions have expanded combustible construction allowances significantly. Confirm the adopted edition.

Exceptions and allowances

The code permits specific combustible materials within noncombustible buildings — each exception has conditions that must be met.

Work through it in this order

  1. Determine the building height, area, and occupancy to identify whether noncombustible construction is required.
  2. Review the NBC definition of noncombustible material and noncombustible construction.
  3. Identify applicable exceptions that permit combustible components within the noncombustible building.
  4. Verify each exception's conditions for the specific material, location, and application.

Common questions

How is a noncombustible material defined?

A noncombustible material is one that meets the criteria of CAN/ULC-S114 or equivalent test standard. The definition is performance-based, not a list of specific materials.

Can wood be used in a noncombustible building?

Limited combustible materials including wood are permitted in noncombustible buildings under specific code exceptions. Each exception has conditions for size, location, and fire protection. Mass timber provisions in recent editions have expanded wood use significantly.

What determines whether combustible or noncombustible construction is required?

Building height (in storeys), building area, and occupancy classification together determine the required construction type through the NBC height and area tables.