Are duplexes soundproof?

A duplex's soundproofing effectiveness varies significantly based on its construction, but here's what you need to know about duplex acoustics:

Typical Sound Transmission Points:

1. Common Walls

• Must meet minimum NCC requirements (BCA)

• Requires minimum Sound Transmission Class (STC) rating

• Need special attention to reduce impact and airborne noise

  2. Critical Areas

• Party walls between units

• Floors/ceilings (for stacked duplexes)

• Plumbing and service areas

• Shared ducts or cavities

Standard Requirements:

1. NCC Specifications

• Minimum STC rating of 50 for walls between units

• Impact isolation rating requirements for floors

• Higher requirements for wet areas and service zones

Common Soundproofing Methods:

1. Construction Techniques

• Double stud walls with cavity

• Acoustic insulation batts

• Resilient mounts for plasterboard

• Mass-loaded vinyl barriers

  2. Problem Areas to Address

• Electrical outlets (should not be back-to-back)

• Plumbing penetrations

• Air vents and ducting

• Door and window locations

Enhancement Tips:

1. During Construction

• Use acoustic sealants at all joints

• Install sound-rated doors where needed

• Consider floating floors for upper levels

• Use vibration isolation for mechanical equipment

  2. Post-Construction Options

• Add mass-loaded curtains

• Install acoustic panels

• Use rubber mats under appliances

• Add weatherstripping to doors

While modern duplexes can achieve good soundproofing, complete sound elimination is unrealistic. Success depends largely on:

• Quality of initial construction

• Attention to detail during installation

• Regular maintenance of seals and gaps

• Understanding that some sound transfer is normal