What are the requirements or limitations for nm cable and plastic boxes in a residential 2 hour rated firewall in townhomes. From what I can understand, a 2 hour rated, load bearing wood stud wall between the townhomes, woiuld require conduit for the nm cable. Any one have any info on this?
Residential 2 hour rated fire wall
- Thread starter bkelly
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renosteinke
Senior Member
- Location
- NE Arkansas
With the description you give, it sounds like the entire wall assembly is the fire barrier, and not just one side. That is, the fire rating is obtained by using both wall faces together.
This means rated boxes or enough 'putty pads' to get the rating, sealed penetrations, and no stud bays with penetrations on both sides.
The fire tests simply don't care if the electrical is in pipe or cables. What does matter is what the approved prints specified.
I don't see how 'load bearing' has any relevance to the wiring method either.
This means rated boxes or enough 'putty pads' to get the rating, sealed penetrations, and no stud bays with penetrations on both sides.
The fire tests simply don't care if the electrical is in pipe or cables. What does matter is what the approved prints specified.
I don't see how 'load bearing' has any relevance to the wiring method either.
walton
Member
- Location
- Sacramento, CA
Try looking in the Building Code chapter 7 Fire-Resistance Rated Construction. 712 Penetrations
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I also believe it is not a problem except if the boxes are in the same bay as a box in the adjoining apt.
I would talk to your Structural Inspector to get the particulars about this.
In Oregon it goes kind of like this:
boxes may not exceed 16 square inches,
no more than 100 sq in of membrane penetrations in 100 sq ft of wall area,
boxes on opposite side of partition must be seperated by not less than 24"
you may use other methods per their listing, putty, tested boxes, etc.
There are boxes out there that per their listing may be placed as close as 3 1/2", if I remember correctly they were Allied and Union. You would have to get their documetation to verify this though.
This can be pretty hard to comply with when kitchens are put back to back.
Good luck~
In Oregon it goes kind of like this:
boxes may not exceed 16 square inches,
no more than 100 sq in of membrane penetrations in 100 sq ft of wall area,
boxes on opposite side of partition must be seperated by not less than 24"
you may use other methods per their listing, putty, tested boxes, etc.
There are boxes out there that per their listing may be placed as close as 3 1/2", if I remember correctly they were Allied and Union. You would have to get their documetation to verify this though.
This can be pretty hard to comply with when kitchens are put back to back.
Good luck~
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