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 18.104.22.168. of Division B.)
This article published by the Ontario Government and also this article should be read by anyone contemplating building a secondary suite, also called basement apartment, granny flat, in-law apartment. I will elaborate upon an important item barely noted in the articles – basement apartment soundproofing.
I get calls often from clients inquiring about soundproofing options for basement apartment. Sometime a client calls me at the right time - before he undertakes the construction. Most often people call me after a contractor finished the construction of their basement apartment, but the soundproofing is inadequate.
It is advisable to contact a building acoustics consultant prior to constructing the apartment. It is a lot 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 Sound Transmission Class STC 50 requirement. This is mandated by the Ontario Building Code for new construction. Meeting this requirement will avoid a possible conflict with a municipal building inspector who may not allow a lesser level of soundproofing.
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.
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