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Old 05-27-2012, 11:22 PM   #1
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


Hi all,

I just finished re-drywalling my kitchen ceiling. I cut out for the electrical box and I got pretty close but there is still a considerable half inch gap most of the way around, and wider at the corners. Here's a picture of the box:



I bought two 3M fire caulks, FB-136 (gray) and CP-25WB+ (red). CP-25WB+ is "intumescent" meaning it expands if there's heat. FB-136 is "versatile" which I assume just means versatile. Other than that I don't see much difference except some code compliance (detailed below). Here's a picture of the caulks:



My questions are

Should I fill in that gap between the electrical box and the drywall? I would assume so to prevent against fire right? There is no insulation in the kitchen ceiling.

If yes should I use fire caulk? My concern with that is I assume it will eventually it will become brittle and could fall down from the gap into whatever lamp fixture I'm putting up there, and it could actually create the very hazard I'm trying to prevent.

And also which fire caulk? Why would you use one over the other? The FB-136 gray says it is current to ASTM E136, IBC2003, IRC2003, IRMC2003, IRFGC2003, NPFA 5000. The CP-25WB+ says none of that but it expands on heat contact.

Thanks!


Last edited by Deck; 05-27-2012 at 11:23 PM. Reason: forgot something
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Old 05-28-2012, 07:24 AM   #2
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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Originally Posted by Deck View Post
Hi all,

I just finished re-drywalling my kitchen ceiling. I cut out for the electrical box and I got pretty close but there is still a considerable half inch gap most of the way around, and wider at the corners. Here's a picture of the box:






My questions are

Should I fill in that gap between the electrical box and the drywall?


Thanks!

I would just fix it when you tape the ceiling with compound... per code, the gap cannot be more than 1/8"....


Last edited by stickboy1375; 05-28-2012 at 08:21 AM.
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Old 05-28-2012, 07:39 AM   #3
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


I agree, there's no need to use caulking. I would use hot mud if I happen to have it on site to fill in the bottom part then air seal the box in the attic with spray foam once it sets up.
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Old 05-28-2012, 08:01 AM   #4
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


I agree with the others about the quick setting compound.

It looks like the box has NM clamps and not clamps for MC or AC cables. The correct clamp has a retainer hole that the conductors fit through while holding the redhead in place.
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Last edited by Jim Port; 05-28-2012 at 08:11 AM. Reason: spelling
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Old 05-28-2012, 08:09 AM   #5
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


Fire caulk is typically used in a commercial/industrial setting to seal penetrations in fire rated walls.
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Old 05-28-2012, 08:20 AM   #6
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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I agree with the others about the quick setting compound.

It looks like the box has NM clamps and not clamps for MC or AC cables. The correct clamp has a retainer hole that the conductors fit through while holding the redhead in place.
I think the electrical tape is holding the redhead in place.
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Old 05-28-2012, 08:25 AM   #7
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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I think the electrical tape is holding the redhead in place.
All that darn tape is probably holding the box up.
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Old 05-28-2012, 08:39 AM   #8
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


And the new fixture will require 90 degree C rated insulation which isn't there either.
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Old 05-28-2012, 11:01 AM   #9
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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And the new fixture will require 90 degree C rated insulation which isn't there either.
I was going to mention that, but i knew it wasn't going to change anything.
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Old 05-28-2012, 11:02 AM   #10
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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And the new fixture will require 90 degree C rated insulation which isn't there either.
Whats the degree rating on 3m? because the conductors are wrapped pretty good.
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Old 05-28-2012, 11:16 PM   #11
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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I would just fix it when you tape the ceiling with compound... per code, the gap cannot be more than 1/8"....
Ok thanks I will add some tape around the box. My concern with that was the compound or caulk or whatever could eventually become brittle and fall out. Should I use flat tape or the mesh? I have both.

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All that darn tape is probably holding the box up.
You mean the electrical tape? No way. This is a link to the box I bought. I used two nails to secure it. Although it has a rating of 50lbs it cannot be used for a fan fixture. Why is that? I bought the box that looked the strongest. Just out of curiousity what box can I use for a fan fixture?

Quote:
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It looks like the box has NM clamps and not clamps for MC or AC cables. The correct clamp has a retainer hole that the conductors fit through while holding the redhead in place.
I have no idea what you just said! I have BX cable so I just put it in and clamped it. Do you mean I should have bought this box instead?

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And the new fixture will require 90 degree C rated insulation which isn't there either.
I'm dealing with two old BX cables that have wires insulated with some type of cracking rubber and rope cloth. Some of the exposed insulation outside the metal shield was falling off so I wrapped over all of it with 3M electrical tape.

Last edited by Deck; 05-28-2012 at 11:19 PM.
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Old 05-28-2012, 11:27 PM   #12
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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I would just fix it when you tape the ceiling with compound... per code, the gap cannot be more than 1/8"....
Got a code reference???
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Old 05-28-2012, 11:45 PM   #13
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Should I use fire caulk (and what type) to fill around this drywalled electrical box?


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Got a code reference???
314.21 and since you weren't aware of that one make sure to take a look at 314.20 as well.

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