dshall

ADU question..... fire separation?

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My client has a two story house. The kitchen is on the second floor.  Each level has its own entrance.  I can easily close off the stairs and add a kitchen at lower lever to turn the lower level into a JUNIOR ADU.  

 

Main house on 2nd floor,  JR ADU on first floor.

 

The question is.....  do I need the one hour fire separation between the two units and if so,  any ideas on how to accomplish this?

 

 

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I know this won't help much, but here the building department would like to see (2) 1/2" Type X Gypsum, which with a 2"x10" and 3/4" T&G sub-floor actually gives 2 hours.....but....anyway. The thing our inspectors look for more than the (2) 1/2" layers is the penetrations. Sloppy gaps in light fixtures and floor penetrations from plumbing above get dinged with me more than my details. Fire caulk is MUST, and proper application. I am sure out there that aspect would be the same.

 

Hope that helps you.

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Separate dwelling units always need some level of fire-resistive construction to demise the two occupancies. In Wisconsin we can achieve horizontal separation for a two-family occupancy with:

1. One layer of 5/8" Type-X on the ceiling.

2. One layer of 5/8" Type-X to protect any supporting floor beams and columns.

3. Appropriate draftstopping and firestopping at vertical penetrations.

4. 90-minute dampers at HVAC ductwork penetrations (this is a PITA in a retrofit).

 

A common issue for this type of conversion is when a single HVAC system supplies both units; tenants share the same air, and the same odors, even if the units are on separate heating/cooling zones.

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One layer of 5/8" type x gyp. bd. is all we need for the 1 hour rating at a garage wall with 2x4@16" o.c.. It seems like that would suffice for the fire code/CRC code.

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Thanks guys for the input.  We have all existing conditions so I am hoping the separation was not required through some kind of a loop hole.

 

Not only do I need the separation,  but I also need an STC Rating of 50 between the two dwellings.

 

I think the floor will need to be the3/4" T&G subfloor,  R-19 in floor cavity,  1/2" type x on resilient channels at the ceiling. (I would probably spec 5/8" type x 

 

and then as Alan alluded to 5/8" type 'x' at interior face of wall supporting the one hour floor/ceiling with 7/8" stucco at exterior face.

 

Another key to this is identifying the "APPROVED" assembly number.  The one below calls out for TJI joists.....  

 

Does anybody disagree with this?37179067_ScreenShot2020-12-02at8_04_31AM.thumb.png.a8ea165880b624d9c42aa5aca1b9fe03.png

 

 

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Just now, Richard_Morrison said:

A JADU is not a separate dwelling unit. An ADU is. Therefore, fire separation requirements between a JADU and the rest of the house probably don't apply. As an example: https://www.cityofcalabasas.com/home/showdocument?id=490 But worth checking with the City, rather than here. 

 

Thanks Richard,  that had occurred to me.  Thank you very much.  I will also confirm with the City.

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I haven't had to do that yet but then again all my ADU's are separate detached buildings

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11 hours ago, dshall said:

Another key to this is identifying the "APPROVED" assembly number. 

Does anybody disagree with this?

 

I did some ADU units a couple of years ago on remodel projects involving older construction methods.  In my case the flooring above was diagonal 1x12 planks and not T&G.

 

What I wanted to point out is that, from what I remember, the entire assembly needs to be approved, and that is typically by the specific drywall manufacturer in order for the assembly to be considered to be approved.

 

I am not disagreeing with the statement, merely pointing out what I believe to be even more stringent requirements.  I am also curious what others have come across regarding these matters.

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Since you mention the word "loop hole" here in North Carolina we are allowed to call a separate living area as a "mother-in-law suite". This allows you to have a kitchen without the need to meet the 1 hour fire separation rules. The only thing is anyone living there other then "family" would violate the "mother-in-law" suite rule and then it would be classified as an ADU.

 

I guess the reasoning here in NC is that your family is less likely to sue each other if the apartment burns down than that of a stranger renting the apartment out.

 

Maybe you have something similar where you live in the local zoning/code books.

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