Soundproofing is critical for legal secondary suites in Ontario and increasingly for open-plan main floor conversions. Here’s the technical breakdown.
Key metrics:
- STC (Sound Transmission Class): Airborne sound. OBC minimum for suite separations: STC 43. Target for comfortable living: STC 50-55.
- IIC (Impact Insulation Class): Footstep/impact sound. OBC minimum: IIC 43.
Assembly options for basement suite ceiling (also main floor):
| Assembly | Approx STC | Approx IIC |
|---|---|---|
| Single drywall on wood joists | 33 | 28 |
| Drywall + acoustic insulation | 39 | 35 |
| Resilient channel + double drywall + acoustic insulation | 50-55 | 45-50 |
| Sound isolation clips + double drywall + floating floor above | 55-60 | 52-58 |
Party wall options:
- Resilient channel on existing studs + second drywall layer: STC 45-50
- Staggered-stud on single plate: STC 50-55
- Double-stud (fully decoupled): STC 60-65, sacrifices 4-6" floor space
Flanking paths are the most common compliance failure – sound routes around well-built assemblies through wall plates and framing. Perimeter details are as important as the assembly itself.
GTA costs (2026):
- Resilient channel ceiling + double drywall (per 100 sq ft): $800-$1,400
- Complete suite acoustic package (800 sq ft basement): $12,000-$25,000
Secondary suite and soundproofing questions at home.renovation.reviews