What sound insulation do I need between a suite and the main house in New Brunswick?

Sound insulation between a secondary suite and the main house in New Brunswick must meet National Building Code requirements, which specify a minimum Sound Transmission Class (STC) rating of 50 for separating walls and floors. This ensures reasonable privacy for both the homeowner and tenant while complying with provincial building standards.

The NBC 2020 edition (adopted in New Brunswick, effective May 1, 2025 for new applications) requires this STC 50 rating for all demising assemblies between dwelling units. This applies whether you're converting existing space or building new. Your local building inspector — either municipal or Regional Service Commission depending on your location — will verify compliance during the permit review and inspection process.

Wall assemblies that typically achieve STC 50 include a standard 2x4 stud wall with 5/8" drywall on both sides, batt insulation in the cavity, and staggered studs or resilient channels. For better performance, consider double-wall construction (separate 2x4 walls with a small air gap) or 2x6 framing with additional insulation. The key is breaking the direct connection between surfaces that would transmit sound vibrations.

Floor/ceiling assemblies are more challenging since they must support structural loads while blocking sound transmission. A typical approach uses 2x10 or engineered joists with 5/8" drywall ceiling below, batt insulation between joists, and resilient channels to decouple the ceiling from the structure. The subfloor above often includes additional underlayment or floating floor systems to reduce impact noise from footsteps.

Professional installation is strongly recommended for sound-rated assemblies. Gaps around electrical boxes, HVAC penetrations, or poorly sealed joints can dramatically reduce performance — even small air leaks can drop your STC rating by 10+ points. Licensed contractors understand the critical details like acoustic caulking, proper insulation installation, and maintaining continuous air barriers.

Before starting any secondary suite conversion, contact your local building permit office first. In incorporated areas like Moncton, Saint John, or Fredericton, reach out to the municipal planning department. In rural areas, contact your Regional Service Commission. They'll confirm zoning compliance and outline the specific permit requirements for your area — secondary suite rules vary significantly across New Brunswick municipalities and RSCs.

The building permit application will require detailed drawings showing your sound-rated wall and floor assemblies. Your contractor or designer should specify the exact materials and construction methods to achieve the required STC 50 rating, which the building inspector will verify during framing and drywall inspections.