Sound Transmission In Attached Homes

No matter how well you get along with your neighbours, you don't want to hear them from inside your new home. 

Several measures can be taken to reduce sound transmission through walls and floors of adjoining residential units.

The Ontario Building Code (OBC) 2012 sets minimum standards for sound transmission and fire resistance in multi-unit construction.  The OBC requires that party walls and floor assemblies separating residential dwellings provide a minimum Sound Transmission Class (STC) rating of 50 and a Fire-Resistance Rating (FRR) of at 45 minutes to one hour, depending on the specific construction.

Typical floor and wall assemblies are pretested and typical STC and FRR ratings are listed in the Ontario Building Code (OBC) 2012 in Supplementary Standard SB-3.  As such, these assemblies can be readily selected to meet most construction needs.

The party wall at our latest infill development is constructed of two separate wood stud walls separated by an air space.  The two walls include a total of six layers of 5/8" type x firecode drywall.  The air space between the walls reduces the transfer of vibrations from one unit to the other.  As the name implies, the absorptive material absorbs sound, while resilient channels decouple the drywall from the wood framing to minimize sound transmission.

A cross-section of the party wall at our latest infill development consists of:

  • 2 layers 5/8 type x firecode drywall
  • resilient channels @ 16" O.C. horizontal
  • 2x4 @ 16" O.C. wood studs
  • sound absorptive mineral wood insulation
  • 1 layer 5/8 type x firecode drywall
  • 1" air space
  • 1 layer 5/8 type x firecode drywall
  • sound absorptive mineral wood insulation
  • 2x4 @ 16" O.C. wood studs
  • resilient channels @ 16" O.C. horizontal
  • 2 layers 5/8 type x firecode drywall

Each of these two walls provides an STC rating of 51 and a FRR of 1 hour.  Therefore, one of these walls alone exceeds minimum code requirements for sound transmission and fire resistance rating required between residential occupancies.

Sound transmission from impact sounds such as footsteps can be disruptive.  In addition to sound absorptive material and resilient channels, sound transmission through floor systems can be improved by using stiffer floor joists.  At our upcoming multi-unit development on Tremblay Road, we are using 12" deep joists where 9.5" joists would have met minimum code requirements in most locations.

A sound test was performed on site by producing a loud noise in one unit and measuring sound in the adjoining unit using a decibel meter.  Watch video below:

A link with a Decibel Equivalent Table