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OBC DIVISION B · PART 9 · SECTION 9.11 — SOUND TRANSMISSION

What STC rating is required between dwelling units in Ontario?

Walls and floors separating one dwelling unit from another, or from common spaces, must achieve a sound transmission class (STC) of at least 50. Assemblies next to elevator shafts or refuse chutes require STC 55.

Code reference
Construction separating a dwelling unit from another unit or from spaces elsewhere in the building must provide a sound transmission class rating of not less than 50, determined by measurement or by using rated assemblies from referenced tables. Separations from elevator hoistways and refuse chutes require a rating of not less than 55.
OBC Division B, Subsection 9.11.2.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

STC 50 applies to demising walls in duplexes, townhouses, and between a basement apartment and the main unit, including the floor assembly, which is the hardest part of most conversions. Ratings come from tested assemblies, such as those catalogued in Supplementary Standard SB-3, so you must build the listed assembly exactly: layer counts, insulation, and resilient channels all matter. Note that STC only addresses airborne sound; footstep (impact) noise is not regulated but drives most tenant complaints, so consider it anyway.

Plain language

Where two homes share a wall or floor, the construction must block enough airborne noise to score at least STC 50, roughly meaning loud speech next door is inaudible. Near elevators or garbage chutes, the bar rises to 55.

Related questions

How do you build a wall or floor that meets STC 50 in Ontario?

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.