What does the OBC say about sound separation when converting a single-family home to a duplex in Ottawa?

When converting a single-family home to a duplex in Ottawa, the Ontario Building Code requires that all walls and floor-ceiling assemblies separating the two dwelling units achieve a minimum STC 50 for airborne sound and IIC 50 for impact sound. These requirements are found in OBC Part 9, and they apply in full to duplex conversions — the City of Ottawa does not grant exemptions simply because the building is existing construction. You will need a building permit for this type of conversion, which you can apply for through 3-1-1 or ottawa.ca, and the sound separation requirements will be part of your permit conditions.The challenge with duplex conversions in Ottawa is that most single-family homes were never built with sound separation in mind. A typical interior wall in a 1970s Kanata bungalow or a 1990s Barrhaven two-storey might have standard 2x4 framing with fibreglass insulation and half-inch drywall on each side — an assembly that tests around STC 33–38, well below the required 50. Bringing that wall up to code requires a significant upgrade. The most common approach is adding resilient channel ($1.50–$2.50 per linear foot) on one side, filling the cavity with Roxul Safe'n'Sound mineral wool ($1.20–$1.80 per square foot), and installing two layers of 5/8-inch Type X drywall with Green Glue compound ($15–$22 per tube) between them. This assembly, properly installed and sealed, can achieve STC 55–60 and satisfies both the sound and fire-rating requirements.Floor-Ceiling Assemblies Are the Harder ProblemIf your conversion creates an upper and lower unit — which is the typical layout for Ottawa side-splits and two-storey conversions — the floor-ceiling assembly between units must meet both STC 50 and IIC 50. Impact sound (footsteps, dropped objects, furniture movement) is harder to control than airborne sound, and the existing floor structure in most Ottawa homes provides virtually no impact isolation. A proper floor-ceiling upgrade typically involves sound isolation clips ($4–$7 each) and hat channel on the ceiling below, mineral wool insulation in the joist cavity, a double layer of drywall on the ceiling, and a floating subfloor or acoustic underlayment above. Budget roughly $15–$25 per square foot for the ceiling treatment and $3–$6 per square foot for the floor underlayment.The total soundproofing cost for a typical Ottawa duplex conversion — covering the demising wall plus the floor-ceiling assembly — usually runs $15,000–$35,000 depending on the size of the separation area and the existing construction. This is a significant line item, but it is not optional, and failing to meet the STC and IIC requirements will mean failing your building inspection and potentially having to redo work. Given the complexity of meeting code requirements in existing construction, this is a project where professional expertise pays for itself. An experienced soundproofing contractor can assess your existing structure, recommend the most cost-effective approach, and ensure you pass inspection the first time. The Ottawa Contractor Directory can help you find professionals with duplex conversion experience in the Ottawa market.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:613BinsRenoMotion Inc.Nic’s D.U.C.T Works IncSteven Labelle - Your Complete Home RenovatorTiptop ContractingView all contractors →