What OBC section covers the minimum STC requirements for floors between dwelling units?

The minimum STC requirements for floors between dwelling units are covered in the Ontario Building Code, Part 9, Section 9.11 — Sound Control. Specifically, OBC 9.11.1.1 establishes that floor-ceiling assemblies separating dwelling units must achieve a minimum Sound Transmission Class (STC) of 50 for airborne sound. The same section also requires a minimum Impact Insulation Class (IIC) of 50 for impact sound, which addresses footfall noise, dropped objects, and other structure-borne sounds that travel through floor assemblies. Both ratings apply to the field-tested (installed) performance, not just the laboratory rating, which is an important distinction because field performance is typically 3–5 points lower than laboratory results due to flanking paths and real-world installation conditions.Understanding what these numbers mean in practice helps Ottawa homeowners set realistic expectations. An STC 50 floor means that normal speech in the unit above will be barely audible below — you might hear muffled voices but not make out words. An IIC 50 floor means that normal walking in hard-soled shoes will be faintly audible but not intrusive. These are minimum standards, and many acoustics professionals consider them barely adequate for comfortable living. If you are soundproofing a floor-ceiling assembly in an Ottawa townhouse in Orleans, a Centretown condo conversion, or a duplex in Hintonburg, targeting STC 55–60 and IIC 55–60 will give you noticeably better quality of life for a modest increase in project cost.Meeting the Standard in Real Ottawa ConstructionA standard wood-framed floor-ceiling assembly with no soundproofing treatment — just joists, subfloor, and a single layer of drywall below — typically tests around STC 32–38 and IIC 28–34, far below code requirements. Reaching STC 50 and IIC 50 requires a combination of strategies. For the airborne sound (STC) component, you need mass and decoupling: mineral wool insulation like Roxul Safe'n'Sound in the joist cavity, sound isolation clips ($4–$7 each) with hat channel on the ceiling, and two layers of 5/8-inch Type X drywall on the ceiling. Adding Green Glue compound between the drywall layers provides additional damping. For the impact sound (IIC) component, you need a resilient layer in the floor above: an acoustic underlayment or floating subfloor system at $3–$6 per square foot makes the difference between a floor that transmits every footstep and one that provides genuine privacy.The total installed cost for a code-compliant floor-ceiling assembly in Ottawa typically runs $12–$22 per square foot, or roughly $8,000–$18,000 for a typical basement ceiling or floor between units in a duplex conversion. It is worth noting that the OBC also references Section 5.9 of Division B for sound control in buildings of larger scope, but for most Ottawa residential projects, Part 9 Section 9.11 is the governing section. For precise specifications tailored to your floor structure and performance goals, consulting with a soundproofing professional who knows Ottawa construction types is the most reliable path forward — the Ottawa Contractor Directory is a practical starting point for finding that expertise.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:Luxe Painting and Renovations JC CarpentryComfort Zone InsulationREJUVENATION RENOVATIONSALM Construction & Landscaping Inc.View all contractors →