Are there specific Toronto bylaws about soundproofing drywall requirements for basement apartments near neighbours?

Yes — if you are creating a basement apartment (secondary suite) in Toronto, the Ontario Building Code imposes strict sound transmission requirements that directly dictate how the drywall assemblies between units must be constructed. These are not optional guidelines — they are enforceable code requirements that building inspectors will verify during the permit inspection process.

The Ontario Building Code requires a minimum STC 50 (Sound Transmission Class 50) rating for wall and floor/ceiling assemblies separating dwelling units, including basement apartments. This means the floor/ceiling assembly between your main-floor living space and the basement apartment below must achieve at least STC 50, and any shared walls between units must meet the same standard. STC 50 means that loud speech from the adjacent unit is barely audible — normal conversation should not be heard through the assembly.

To achieve STC 50 in a floor/ceiling assembly separating a main floor from a basement apartment, a typical code-compliant drywall assembly in the GTA includes 5/8-inch Type X drywall on the basement ceiling mounted on resilient channel (hat channel spaced 16 or 24 inches on centre, perpendicular to the joists), with batt insulation (R-20 minimum) filling the joist cavities. The resilient channel is critical — it decouples the drywall from the floor joists, breaking the direct path for sound vibration. This assembly typically achieves STC 50–55 when properly installed. Adding a second layer of 5/8-inch drywall with staggered joints, or using Green Glue compound between double layers, can push the rating to STC 55–60.

The City of Toronto has been actively encouraging secondary suites since the adoption of the Municipal Code Chapter 150 provisions for second suites, and the city's zoning bylaws now permit secondary suites in most residential zones. However, every secondary suite requires a building permit, and the sound separation requirements are a key part of what inspectors check. The permit process includes review of your proposed wall and ceiling assemblies to verify they will meet or exceed STC 50.

For shared walls between the basement apartment and adjacent living spaces within the same building, the same STC 50 requirement applies. A standard assembly that meets this requirement is a staggered-stud or double-stud wall with insulation in the cavity and 5/8-inch drywall on each side. A single-stud wall with resilient channel on one side and insulated cavity can also achieve STC 50, but staggered or double-stud walls provide better real-world performance because they eliminate the rigid connection between the two drywall surfaces entirely.

Fire separation is equally important — the Ontario Building Code requires a minimum 45-minute to 1-hour fire resistance rating between dwelling units. This means 5/8-inch Type X drywall is required on the ceiling and shared walls of the basement apartment, with all joints properly taped and finished. The fire-rating and sound-rating requirements work together — the assemblies that achieve good fire separation (double Type X drywall, insulated cavities) also contribute to better sound performance.

The cost to properly soundproof a basement apartment ceiling in the GTA runs $5.00–$10.00 per square foot for the drywall, resilient channel, insulation, and finishing. For a typical 700-square-foot basement apartment, that translates to roughly $3,500–$7,000 for the ceiling assembly alone. The shared walls add another $2,000–$5,000 depending on the wall area and assembly type. These costs are significantly higher than standard drywall installation because of the resilient channel, double layers, and the precision required — a single screw driven through the resilient channel directly into a joist (called a "short circuit") defeats the entire sound isolation system.

Common mistakes that fail inspection include using standard 1/2-inch drywall instead of 5/8-inch Type X (fails both fire and sound requirements), omitting resilient channel, leaving gaps in the insulation that create sound flanking paths, and running rigid ductwork or plumbing through the assembly without proper acoustic isolation. GTA building inspectors are experienced with secondary suite conversions and know exactly what to look for.

This is absolutely a hire-a-professional project. The drywall assemblies must be designed to meet code, installed with precision, and inspected before and after drywall installation. A professional drywall contractor experienced in Toronto secondary suite conversions will know the required assemblies and can coordinate with the other trades to ensure the sound and fire separations are maintained throughout the build. Find local drywall professionals through the Toronto Construction Network who have experience with basement apartment projects.