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Sound transmission class (STC) is the rating system used to measure a partition wall’s ability to reduce the effect of airborne sound. A higher STC rating means less sound will make its way through the partition wall – sometimes called a party wall, common wall or shared wall – creating a quieter living space.

If you’ve ever lived in an apartment or townhome where you can hear your neighbours’ every move, you know how irritating it can be. However, many homebuyers don’t know about STC ratings or the importance of asking about them before making a purchase.

If you’re interested in living in an attached or multi-family home, STC ratings should be top of mind during your house hunt. If you have a noisy furnace that wakes you up every hour, you’d replace it, right? Unfortunately, it’s not as easy or cost-effective to replace a wall.

Unless you have the express interest and permission of the neighbouring party to replace a common wall – and don’t mind intense construction and limited privacy between suites for a time – it’s pretty much impossible. The cost of fixing a common wall can be over 10 times the cost of doing it right in the first place. Even then, you might never achieve the STC rating you desire.

Typically, the higher the STC rating, the better. Higher STC ratings mean the shared wall separating you from your neighbours has a greater ability to reduce sound transmission.

Courtesy of Millenium Plus Homes

In Canada, the minimum requirement for walls and floors between dwelling units is 50 STC. Some rooms or dwellings may require higher STC ratings, such as government offices or boardrooms.

If you’re home-shopping, here’s a rough guide to STC ratings you can use as a reference:

  • Poor: 30-39 STC
  • Good: 40-49 STC
  • Great: 50-59 STC
  • Excellent: 60-67 STC

If you’re building a new home, you have full control over the STC rating. Our standard for party walls is an STC rating between 59 and 67. It’s extremely important to us that anybody who lives in the homes we build gets to enjoy their own home’s freedom and privacy.

Considerations when constructing a party wall include proper insulation, stud arrangement, stabilization, and how the units are attached to each other. They also need to be up to fire code. Discussing these points with your builder, REALTOR® or landlord is important if you’re looking to purchase or rent a new home.

For many, the exterior, cabinets, tile, hardwood, and other finishings are what create value when purchasing or building a home. Few are concerned about how well your unit will protect you from unwanted noise. Whatever your situation, be sure to ask about STC ratings – they can affect your life more than you think.

Shameer Gaidhar is president and CEO of Millenium Plus Homes