ADU question..... fire separation?

[dshall]

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?

 

 

[joey_martin]

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.

[rlackore]

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.

[Gawdzira]

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.

[dshall]

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?

 

 

[Richard_Morrison]

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. 

[dshall]

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.

[DRAWZILLA]

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

[RodCole]

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.

[ShaneK]

[misterwiley]

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.

[dshall]

Yeah,  I still do not have an answer for this.

 

I am looking for a 1-hour Wall Assembly with an STC50 and IMPACT class of IIC using 2x10's @ 16" oc.

 

Does anybody have this detail handy?

 

If you do,  thank you.......  (I already have the existing condition of 3/4" ply on the 2x10 @ 16,  I would rather not add anything on top of plywood since it is an existing condition.  I can do anything at bottom of floor).

 

 

[JKEdmo]

16 minutes ago, dshall said:

Wall Assembly

Do you mean floor assembly?

[dshall]

Just now, JKEdmo said:

Do you mean floor assembly?

Yes,  I mean floor assembly,  thank you

 

[JKEdmo]

28 minutes ago, dshall said:

Yeah,  I still do not have an answer for this.

 

I am looking for a 1-hour Wall Assembly with an STC50 and IMPACT class of IIC using 2x10's @ 16" oc.

 

Does anybody have this detail handy?

 

If you do,  thank you.......  (I already have the existing condition of 3/4" ply on the 2x10 @ 16,  I would rather not add anything on top of plywood since it is an existing condition.  I can do anything at bottom of floor).

 

 

 

Does this get you close?  Taken from Gypsum Assoc. Fire Resistance Design Manual, 19th Edition.

 

If not, there are other systems in there that might work.

 

Jim

 

 

[Gawdzira]

[Gawdzira]

acoustic-wall-assemblies-catalog-techincal-guide.pdf safensound-fire-and-soundproofing-insulation-techdata.pdf

[dshall]

Thanks Jim & Alan (appreciate the link to the catalogs.) Hey and they won't put what are you doing it's like us interfere go to system living assisted living in a house in the house in the house in my house yeah you yeah you don't have to go to the assistant he said he'll come in do the service 48 eight your house gotcha thanks very much I have to get well hello

 

These are the assemblies that come close....  the big hang up is we are putting a JADU under an EXISTING FLOOR ASSEMBLY and we we trying to avoid adding an extra layer of the existing 3/4" ply sub floor.

 

I think my client will need to put an extra layer of something on the existing floor assembly above the new JADU.

 

Thank again.,

 

[Gawdzira]

Also, if you are putting a layer of ply above, you can look at fire rated ply. I am not sure how stinky it would be for out-gassing? The other thing you may be able to work with on the underside are intumescent paints. But, I think the fire path is both directions thus needing fire resistant materials each side. 

[JKEdmo]

27 minutes ago, dshall said:

These are the assemblies that come close....  the big hang up is we are putting a JADU under an EXISTING FLOOR ASSEMBLY and we we trying to avoid adding an extra layer of the existing 3/4" ply sub floor.

Good luck!  Probably not possible as a tested assembly, but could be wrong.  You might be able to convince the building official to accept an "equivalent" custom detail you propose.

I suspect the floor topping is necessary to achieve the higher impact rating.