STC vs fire rating for legal basement apartment

10/9/2022 at 10:13:47 PM

If the OBC is the same as Alberta (which is likely) there is no requirement for fire rated drywall for a secondary suite, only regular 1/2" which offers a 10 minute rating. Newly introduced in this Code cycle (2019) is a requirement for STC which is lower for a secondary suite, 43 compared to 50 for a normal separation between dwelling units. There are tables in the Code with various assemblies and their respective fire and sound resistance ratings including single or double drywall, resilient channels, etc. etc. The simplest assembly that meets STC 50 is conventional wood frame construction and floor sheathing, resilient metal channels spaced 400 mm o.c. and 2 layers of 1/2" Type X drywall for an STC of 51 and a fire resistance rating of 1 hr. Keep in mind that this assembly does not take into account flanking paths of sound transmission and it is therefore recommended to go beyond STC 50 to account for these paths. To find out the common practice best thing to do is look at some show-homes in your area that come with a finished secondary suite. The Alberta Building Code is a free download for a single user.

10/10/2022 at 3:52:22 PM

Hi I'm Odel from karsan and Philip wall and ceiling Inc, good question.I compare gas fitting and plumbing to fire rating and STC ,why 5/8 type X drywall has a fire rating and sound rating as well so double up the board, you maximize both fire and sound and adding reverberating channels does not give and over kill,it gives the Manufacturer standard space between the Joice or studs to do it's job Maintaining soundproofing and fire rating with out being an overkill.the only thing that can make it Questionable is if there is insulation in either walls or ceiling .Regular insulation can be replaced with safe and sound and if the wall or ceiling Does call for insulation this cannot be an overkill because it would already be a part of the design of the wall. Two sheets of drywall five eights tape X gives you 2 hr fire rating , Reverberating channel and safe and sound insulation helps with sound dampening none of these techniques affect the Ontario building codes.Hope this was clear enough to understand or answer your question.

Ps One should always refer to building or house drawing plans.

10/16/2022 at 12:14:07 AM

Check with your local planning and development dept.. It is typically accepted 1/2" for personal use

11/3/2022 at 3:55:56 PM

I found this link after searching 'OBC fire and sound resistance tables':

https://free.bcpublications.ca/civix/document/id/public/bcbc2018/bcbc_2018dbp9rt

The first 25 pages are wall assemblies and then starts floor assemblies. Floor assemblies meeting STC 50 start on Page 34. Again keep in mind you will need to select a higher rated assembly because of 'flanking paths' of sound transmission.

Also found this link:

https://www.townofws.ca/en/residents/resources/Documents/SecondSuitesBuildingCodeDesignGuide.pdf

Interestingly in Ontario the same STC rating (50) is required for secondary suites as between dwellings, different than Alberta (9.11. on Page 11).