Question about converting basement to an apartment re fire separation

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Posted by: from Lindsay
10/3/2018 at 10:48:30 AM

I am thinking of converting basement to apartment. Can the required fire separation be installed under the subfloor upstairs? If I have to rip out the ceiling I'm not going to bother because that it just too expensive. i have to replace upstairs flooring and was wondering if that was a way to install the required fire separation?

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Date/Time10/3/2018 at 12:07:01 PM


Yes you can put a fire wall under the subfloor there are only a few rules we have to follow.


Faizan Alam

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Date/Time10/3/2018 at 12:37:08 PM

If you presently have 1/2" drywall on your ceiling in the basement , just add another layer of drywall to what's there ( Your cheapest option ) or you may have to install a layer of fire rated drywall. Talk to your local Building Inspector. There could be a few other restrictions your not aware of.

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Date/Time10/3/2018 at 12:50:49 PM

Converting your basement into a mortgage helper is a great idea. To answer your question, it depends on whether or not you want to make this a legal suite or not. If you want everything by the book then it would be best to actually contact your local municipal building department to make sure that you meet all of their specific requirements.

In short answer to your initial question however, fire separation is for the purposes of slowing fire spreading to the rest of the house. It also helps to protect the structural components such as your flooring joists. That's why you would need to add the fire separation from below.

You may be able to add another layer of drywall without removing the existing materials. However often it is warranted to expose the underside for the purposes of sound proofing, adding extra lighting and in some cases replacing old water lines that are poly-b which is known to leak after a number of years.

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Paul from PJV Contracting in Kamloops
Date/Time10/3/2018 at 1:10:13 PM

Hi Kristy,

In my experience in new home apartment construction, I have never seen / heard of the fire separation assembly under the upper unit sub-floor. This solution (if it exists, though I don't see how it would work) would seem to be a far more expensive solution than adding a layer 5/8 drywall ceiling below. Regardless if you are replacing the flooring, pulling-up a sub-floor (if correctly installed) is a very difficult task as the sub-floor should be nailed and glued in-place.

That alone may not be enough to achieve the required rating (but should be), in addition to a double layer of drywall, we poured an 1 1/2 of light-weight concrete/gypcrete on the floors, which may have been part of the fire rating assembly.

The ceiling joisting / framing is what needs to be protected from ignition, additionally any penetrations between floors/dwellings (plumbing, electrical, low voltage) need to be fire-caulked. BC building code requires a one hour fire rating assembly between floors if the suite is on the lower level of a 2 story structure, 45 min rated firewall if the suites are side to side. 5/8 type X drywall has a one hour fire rating, regular 1/2 drywall has a 1/2 hour fire rating.

Truth is, the only qualified individuals who could answer your question properly is an architect or code consultant who is familiar with your local municipal /provincial fire/building codes.

You will get a bunch of different answers from contractors, just remember this has liability written all over it, best hire an architect or code consultant to review all legal elements of converting the space to an apartment/suite/secondary suite and let them assume all the liability.

*Edit* Your local building inspector, municipality will NOT (and should not) be able to help with this other than to tell you that it needs to be in compliance to your provincial building code, BC Fire code, and national fire code. A building inspector will only sign-off on completed works based on architectural, structural drawings and often based off of a technical field inspection report issued by an Architect or P.Eng. If an inspector gives you directions on how to achieve the fire rating, then he/she is performing a service outside the scope of his/her work. Even BC Building code safety bulletins (which document exactly what is required) have legal disclaimers on them. Call an architect or code consultant.


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Date/Time10/3/2018 at 6:05:30 PM

All you need is drywall for a fire separation it's really only a smoke stop and this is required by all municipalities. I recommend you installing 5/8 fire-rated drywall on the basement ceiling and you are good to go it regardless of what flooring you use upstairs. I recommend you put safe and sound insulation in between the floor and the ceiling as well not only for Firestop but for noise-proof. Jeff

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Date/Time10/3/2018 at 9:19:40 PM

Hi There,

Installing under subfloor doesn't separate Basement level to main level,just doesn't do anything.

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Date/Time10/4/2018 at 12:21:52 AM

My understanding is your inquiry is with respect to an Ontario municipality (Lindsay). All Codes are based on the National Building Code with most provinces adopting some minor revisions.

Secondary suites were introduced into the National and subsequently the Alberta Building Code in 2006 (two Codes ago). Before then fire separations were required.

With the introduction of secondary suites some relaxations occurred, and in fact no fire separations are required, only fire stops - regular 1/2" drywall which gives approximately 10 minutes of protection; whereas the lowest fire resistance rating is 1/2 hr. There are tables in the Code of various assemblies demonstrating how to achieve fire resistance ratings and they all show the protection beneath the structural elements. The drywall is required not only to protect the structural elements but also throughout the home as an interior finish meeting the required flame spread rating of 150.

In Alberta you can get Code advice from your municipality when applying for a building permit without the need for a 'Code consultant'.

Other requirements for secondary suites include completely separated ventilation systems (no mixing of air from suite to suite), fire protection to the mechanical room (with taped joints), additional smoke and CO alarms; just a few things to consider.

First step in the process is a development permit assuming you are going for a legal suite.

Ian Derksen Safety Codes Officer - Building

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