Residential 1 hour ceiling

[Horst]

So, we have a new type of "duplex" (city calling it that) and they are stacked. 1st floor is one unit, second is the 2nd unit. The floor of the top unit is 3/4" gypcrete on 3/4plywood over scissor truss, then hat channel and 5/8" sheetrock. This entire assembly is designed as a 1 hour fire separation. We are using Tenmat caps over all of our recess cans https://www.tenmatusa.com/fire-rated-light-enclosures/ff109-300-ul-fire-rated-recessed-light-cover/ and have built 12 of these so far. Inspector came in today and says we need to wire them in MC because we are in the fire "cavity". Keep in mind these are wired in NM, the NM goes through the vent that tenmat provide for this reason, and it is fire foamed at each location where it goes to the switch box. I have racked my brain, researched everything to no avail. I have used NM in this application for years in both walls and ceilings (although ceiling less common) Not that this makes it right, and I cannot even justify with the NEC.... So.... we wire in MC from now on?

 

[hbiss]

While I agree that there seems to be nothing in the Code to prohibit the use of NM in your situation (IE: a fire rated 2 family demising partition), my opinion is that the Code is very lenient with the allowable uses of NM. I think your inspector is thinking the same thing and I agree with him. But he needs to have some kind of local amendment to back it up, not just his say so.

-Hal

 

[Horst]

Thank you Hal, I agree. And what is funny is you are the only reply, people stayed away from this one like the plague! I guess we will humor the AHJ for now until I can get a better grip on my argument. I am not usually stumped, and when I am this forum usually comes to my rescue! Not today I am afraid!

 

[hbiss]

Thank you Hal, I agree. And what is funny is you are the only reply, people stayed away from this one like the plague!

Nahh, they just know that I'm always right. :happysad:

-Hal

 

[roger]

You are looking in the wrong place for help, it is not in the NEC it will be in the UL Fire Resistance Directories (Orange Books) specifically the "Through Penetration Assemblies", for example

http://productspec.ul.com/document.php?id=XHEZ.W-L-3001

The manufacturer of the product shows NM being used in their installation video and you could contact them for more information, I would.

Roger

 

[hbiss]

You are looking in the wrong place for help, it is not in the NEC it will be in the UL Fire Resistance Directories (Orange Books) specifically the "Through Penetration Assemblies", for example

http://productspec.ul.com/document.php?id=XHEZ.W-L-3001

The manufacturer of the product shows NM being used in their installation video and you could contact them for more information, I would.

Roger

I don't think the inspector is talking about firestopping, but the use of NM in this instance for the same reasons it's not allowed in type I and II construction.

-Hal

 

[Sean G612]

He's just dead wrong
The tenmat" fire cap" is designed to keep the fire, any fire from penetrating through it, for Up to 2 hours, regardless of the wire run to your lights under that cap
The prior use of the Tenmat means you've created your own Fire proof Protective she'll
The NM Wire or the Mc make no difference ,Flame and smoke spread from a fire below is contained Under your Continuous fire membrane assembly and subsequent use of your Fire Caps ....Period....
MC use in Fire ratings is In Places of assembly and where Occupancy or Height increase the need for longer fire burn through times, better protected wire from animals, damage and other issues
Nm.-b
Is good for up to 4 story R2 use which is what your duplex is.

 

[Sean G612]

#1
Just a silly question
Using Halo 245R ICT in a fire rated ceiling is Illegal, but if you wrapped them in 3m Fire putty pads wouldn't that give you a 1 hour fire rating in a single 5/8" gypsum ceiling membrane?

 

[Fred B]

While I agree that there seems to be nothing in the Code to prohibit the use of NM in your situation (IE: a fire rated 2 family demising partition), my opinion is that the Code is very lenient with the allowable uses of NM. I think your inspector is thinking the same thing and I agree with him. But he needs to have some kind of local amendment to back it up, not just his say so.

-Hal

Many times local or state code can go above (stricter) the NEC. Check with officials for code reference or unique circumstances that would require NM, not arguementative but present as fyi, for future use and to present to HO or Employer to justify added cost. If legitimate, they (inspectors) love to show off knowledge, if not they simply get angry. You can just do it their way this time because next time it likely will be different, or if you feel it worth it, fight it by going over their heads (May be repercussions doing that).