What is a secondary suite?
Ontario building code definition of a secondary suite (basement apartment): Secondary suite means a self-contained dwelling unit with a prescribed floor area located in a building or portion of a building of only residential occupancy that contains only one other dwelling unit and common spaces, and where both dwelling units constitute a single real estate entity. (See Appendix A and Article 9.1.2.1. of Division B.)
More...
The Ontario Government published an article about basement suites. The article should be read by anyone contemplating building a secondary suite, also called a basement apartment, granny flat, or in-law apartment. Finally, I will elaborate upon an essential item barely noted in the articles – basement apartment soundproofing.
Soundproofing requirements
I often get calls from clients inquiring about soundproofing options for a basement apartment. Sometimes a client calls me at the right time - before he undertakes the construction. However, people often call me after a contractor finishes the construction of their basement apartment, but the soundproofing is inadequate.
I suggest contacting a building acoustics consultant before constructing the apartment. It is much cheaper to do the job right than redo it when the soundproofing is proven inadequate.
What level of soundproofing is required for basement apartments?
I recommend building the basement apartment to meet the Sound Transmission Class STC 50 requirement. This is mandated by the Ontario Building Code for new construction. Meeting this requirement will avoid conflict with a municipal building inspector who may not allow a lesser level of soundproofing.
Basement Apartment Soundproofing Advisory Guide
Soundproofing a basement apartment is one of the most common concerns for homeowners and property managers. Proper planning and execution are crucial to preventing noise complaints and ensuring a comfortable living environment.
1. Consult Early: The Key to Success
Timing matters: The ideal time to involve a building acoustics consultant is before construction begins.
Why it’s important: Early consultation ensures walls, ceilings, floors, and mechanical systems are designed to minimize airborne and structure-borne noise.
Cost-benefit: Incorporating soundproofing during construction is much cheaper and more effective than retrofitting after the fact. Retrofitting can be costly, disruptive, and may not achieve the desired results.
2. Common Noise Challenges
After construction, clients often experience problems such as:
Inadequate wall or ceiling insulation leading to music, TV, or speech being audible in neighbouring units.
Structure-borne noise, such as footsteps or furniture movement, is transmitted through floors and ceilings.
Mechanical system noise (HVAC, pumps, water heaters) is causing vibrations and humming.
Gaps or penetrations in walls, floors, or ceilings allow sound to leak.
3. Recommended Pre-Construction Measures
To achieve effective soundproofing, consider these design strategies before construction:
Airborne Noise Control
Use sound-rated wall and ceiling assemblies.
Incorporate mass and damping materials to reduce sound transmission.
Seal gaps around windows, doors, and penetrations.
Structure-Borne Noise Control
Install floating floors or resilient underlayments to reduce vibration.
Use resilient channels or isolation clips to decouple walls and ceilings from the building structure.
Mechanical Noise Control
Isolate mechanical equipment (HVAC, pumps, water heaters) using vibration pads or mounts.
Position equipment away from bedrooms or living areas when possible.
Ensure ductwork does not transmit vibrations or noise through the building.
4. Post-Construction Retrofits (If Needed)
If soundproofing is inadequate after construction:
Retrofitting is possible, but often more expensive and disruptive than planning ahead.
Possible solutions include:
Adding insulation in walls and ceilings.
Installing resilient channels, floating floors, or soundproof panels.
Sealing gaps and improving door or window acoustic performance.
Always consult a building acoustics expert to identify the most effective and efficient measures.
5. Key Takeaways
Prevention is cheaper than cure: Soundproofing should be designed and implemented before construction.
Understand the noise paths: Noise can be airborne, structure-borne, or both. Effective mitigation depends on identifying the source and transmission path.
Professional guidance is invaluable: A building acoustics consultant ensures the solution is cost-effective, compliant with regulations, and truly effective.
A building acoustics consultant will recommend a range of wall and ceiling assemblies that meet or exceed the STC 50 requirement. He will also address other noise issues not directly covered by the building code, such as impact noise, door soundproofing, and HVAC air distribution. The cost of the consultation is a small fraction of the cost of building the basement apartment, and it will help prevent future problems, such as conflicts with a building inspector or inadequate soundproofing.
To contact a building acoustics consultant for a no obligating quote, use the button below.
