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

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

Use a tested assembly, typically double or staggered studs, or resilient channels on one side, with absorptive insulation in the cavity and often double layers of gypsum board, selected from OBC Supplementary Standard SB-3 or manufacturer test reports.

Code reference
Compliance may be demonstrated by constructing assemblies listed with STC ratings in the referenced tables of Supplementary Standard SB-3 or supported by tests to the referenced ASTM methods. The listed rating applies only when the assembly is built as described, including framing configuration, insulation, gypsum board layers and resilient attachment.
OBC Division B, Subsection 9.11.2. and Supplementary Standard SB-3

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

What this means in practice

The classic STC 50+ recipes are: wood studs with resilient channel on one side, cavity insulation, and 5/8-inch Type X drywall (double-layered on at least one side), or a double-stud wall for higher performance. Execution kills ratings more than design: screws hitting studs through resilient channel, back-to-back electrical boxes, unsealed perimeter gaps, and pot lights all short-circuit the assembly. Seal edges with acoustical sealant and offset penetrations. For floors above basement apartments, add insulation, resilient channel, and double drywall to the ceiling below.

Plain language

You reach STC 50 with proven recipes: insulation in the wall or ceiling cavity, springy metal channels so drywall isn't rigidly attached, and extra drywall layers. Sloppy details like gaps or back-to-back outlets ruin an otherwise good wall.

Related questions

What STC rating is required between dwelling units 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.