Canadian building code question

What sound transmission class (STC) rating is required in Canada?

The NBC requires a minimum STC 50 rating for walls, floors, and ceilings separating dwelling units, and STC 55 for separations between dwelling units and common corridors or other non-dwelling spaces.

Sound transmission requirements in the National Building Code protect occupants from noise transfer between dwelling units and between residential and non-residential spaces. These requirements apply to separating assemblies and are measured using the Sound Transmission Class (STC) rating system, with minimum thresholds that vary by the type of separation.

What to check first

  • Walls and floors between dwelling units require a minimum STC 50 rating under NBC Part 9 (or equivalent in Part 3).
  • Separations between dwelling units and corridors, service rooms, or other non-dwelling spaces may require STC 55.
  • Both field-tested (FSTC/ASTC) and laboratory-rated (STC) values are referenced depending on the code edition and provincial adoption.

Jurisdiction notes

National baseline

NBC Part 9 Section 9.11 sets the minimum STC ratings for separating assemblies in residential buildings. Part 5 covers environmental separation requirements including sound.

Provincial variations

Some provinces have adopted higher STC requirements or added impact insulation class (IIC) requirements for floor assemblies. Ontario and BC in particular may have amendments.

Project-specific variables

The type of occupancy on each side of the separation, the assembly construction method, and whether field testing is required all affect compliance.

Work through it in this order

  1. Identify which assemblies in the building serve as separations between dwelling units or between dwelling and non-dwelling spaces.
  2. Determine the minimum STC rating required for each type of separation under the applicable code edition.
  3. Verify the assembly construction meets the required STC rating through tested assemblies or engineering calculations.
  4. Check whether the province or municipality requires field testing (FSTC/ASTC) in addition to design ratings.
  5. Confirm whether impact insulation class (IIC) requirements also apply to floor-ceiling assemblies.

Common questions

What is the minimum STC rating between condos or apartments?

The NBC requires a minimum STC 50 rating for walls and floor-ceiling assemblies separating dwelling units.

Does the code require impact sound ratings for floors?

The NBC does not universally require IIC ratings, but some provinces and municipalities have added impact insulation requirements for floor-ceiling assemblies between dwelling units.

Is field testing required for sound ratings?

The NBC references laboratory STC ratings for design compliance. Some provinces or projects may require field testing (FSTC/ASTC) to verify installed performance.