Does the Ontario Building Code treat airborne and impact sound differently for permit inspections?

Yes, the Ontario Building Code (OBC) treats airborne and impact sound as two distinct performance metrics, each with its own rating system and minimum requirements. Airborne sound is measured using the Sound Transmission Class (STC) rating, while impact sound is measured using the Impact Insulation Class (IIC) rating. Both must meet minimum thresholds in applicable assemblies, but they are evaluated separately because they address fundamentally different noise transmission mechanisms.Airborne sound includes voices, music, television, and any noise that travels through the air and vibrates building elements as it passes through. The OBC Part 9 requires a minimum STC 50 for party walls and floor-ceiling assemblies separating dwelling units in houses, townhomes, semi-detached homes, and low-rise condominiums. This applies to walls between your unit and a neighbour's unit, between a unit and a common corridor, and between a unit and a common amenity space. Impact sound includes footsteps, dropped objects, furniture movement, and any noise generated by physical contact with a building surface that sends vibrations through the structure. The OBC requires a minimum IIC 50 for floor-ceiling assemblies between dwelling units — this applies specifically to horizontal separations where one unit is above another.How Inspectors Evaluate ComplianceDuring a permit inspection in Ottawa, the building inspector does not typically bring acoustic testing equipment and measure STC or IIC values on site. Instead, compliance is demonstrated through assembly specifications — you or your contractor submit wall and floor assembly details that have been laboratory-tested and rated to meet the code minimums. The OBC references tested assembly catalogues, including the National Research Council of Canada (NRC) publications and the Gypsum Association Fire Resistance and Sound Control Design Manual, which list pre-tested assemblies with documented STC and IIC ratings. If your submitted assembly matches a tested configuration that meets STC 50 and IIC 50, the inspector accepts it.The critical distinction for your project is that a wall assembly that achieves STC 50 does nothing for impact sound, and a floor with good IIC performance may still allow airborne sound through if not properly detailed. They require different solutions. High STC comes from mass, decoupling, and damping — think double drywall with Green Glue on resilient channels or isolation clips. High IIC comes from resilient underlayments, floating floors, and soft surface coverings — carpet and pad, rubber underlayment beneath hardwood, or engineered floating floor systems on neoprene isolators. A bare hardwood floor on a standard wood-frame floor might achieve IIC 35 while the same assembly with the ceiling below treated could hit STC 52 — code-compliant for airborne sound but failing badly for impact.In Ottawa's housing stock, this distinction matters particularly for condo conversions in older Centretown buildings, secondary suite additions in Kanata or Barrhaven homes, and townhouse shared walls and floors. If you are renovating a floor-ceiling assembly between dwelling units, you must address both STC and IIC. Simply adding insulation and drywall to the ceiling improves STC but does almost nothing for IIC — you need resilient elements on the floor side or decoupled ceiling systems with sound isolation clips to address impact transmission.When the inspector flags a concern, they are checking that the as-built assembly matches the submitted specification. Common issues include missing acoustic caulk at perimeters, screws that short-circuit resilient channels, unsealed electrical penetrations, and HVAC boots that create rigid connections through the assembly. Each of these errors degrades both STC and IIC performance.For projects where both airborne and impact sound ratings matter, working with a contractor who understands the difference and can specify assemblies that meet both thresholds is essential. The Ottawa Contractor Directory at justynrookcontracting.com/directory can help you find soundproofing professionals who are familiar with OBC requirements and the City of Ottawa inspection process.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:613BinsRenoMotion Inc.Nic’s D.U.C.T Works IncDenys Builds Designs RenovationsOttawa CaulkingView all contractors →