Canadian building code question

What are the building code requirements for soundproofing between units in Canada?

The Canadian building code requires a minimum Apparent Sound Transmission Class (ASTC) of 47 between adjacent dwelling units, replacing the older laboratory-only STC 50 target, with impact noise and provincial overlays adding additional requirements.

Sound between residential units is a frequent source of construction complaints, and the code has tightened expectations through the ASTC measure to better reflect real-world conditions. The right detailing approach depends on whether the wall, floor, or ceiling is in scope and what penetrations are present.

What to check first

  • Confirm the required ASTC rating between dwelling units for the applicable code edition.
  • Address flanking paths, not only the central assembly, since ASTC captures field performance.
  • Coordinate impact sound for floor and ceiling assemblies in addition to airborne sound.

Jurisdiction notes

National baseline

NBC 2015 and later require ASTC 47 between adjacent dwelling units rather than laboratory STC.

Some provinces add criteria

Provincial overlays can adjust impact insulation requirements and certain assembly classifications.

Municipal noise bylaws separate

Soundproofing between units is a building-code question; ambient noise from neighbours and outdoor sources is regulated by municipal bylaws.

Work through it in this order

  1. Identify all demising assemblies between dwelling units, including walls, floors, and ceilings.
  2. Specify assemblies with documented ASTC performance, not just laboratory STC.
  3. Detail flanking paths at junctions, penetrations, and shared services.
  4. Address impact sound separately for floors and ceilings.
  5. Document field performance assumptions in the permit submission.

Common questions

What is ASTC?

Apparent Sound Transmission Class — a field-based measure that includes flanking sound, used by the NBC for between-unit performance.

Is STC still relevant?

STC remains useful for assembly comparison, but the building code now sets the requirement in ASTC terms.

Does the code address impact noise?

Yes, separately from airborne sound, particularly for floor and ceiling assemblies.