Romex wiring between ridgid foam

Ask your electrical related questions here
JasonS
Posts: 6
Joined: Sat Jul 23, 2016 5:21 pm

Romex wiring between ridgid foam

Postby JasonS » Tue May 16, 2017 1:04 pm

Hi I have a ceiling with no lights in it and I would like to add some. I can't get into the addict cause it's a sloped roof. I want to accomplish 2 things better insulate the ceiling and run new track lights in this room. My thought is if it is legal I would run the wiring over the existing drywall stapling it through the drywall into the truss. Then put 2" ridgid foam over the entire ceiling and over the wiring. The drywall over top of the foam board and mud tape paint add lights done. It this allowed in the code?


User avatar
Aaron
Posts: 1089
Joined: Sat Jan 03, 2015 4:03 pm
Location: St. Paul, MN

Re: Romex wiring between ridgid foam

Postby Aaron » Tue May 16, 2017 4:59 pm

You could do what you're planning with either EMT (non-flexible tubing) or Type MC (flexible metal-clad cable) with steel boxes and covers. This is for protection of nail/screw punctures.

Either choice is also acceptable for surface mount, as well. You're right that NM (non-metallic cable) can only be behind drywall.

User avatar
emtnut
Posts: 484
Joined: Mon Mar 02, 2015 7:21 am
Location: Canada
Contact:

Re: Romex wiring between ridgid foam

Postby emtnut » Wed May 17, 2017 1:32 pm

If I'm understanding your set-up .... I don't see a problem as long as you have the 1 1/4" clearance, which you should with the 2" foam.

I've never come across that before ... The main worry I would have is you basically have 2 vapor barriers now, and the inside layer of drywall will be subject to mold ?

Maybe Shannon or Sprucy will comment on that.
~~ I'm right on 34 of 100 answers ... That ties me with Babe Ruth :mrgreen: ~~

User avatar
emtnut
Posts: 484
Joined: Mon Mar 02, 2015 7:21 am
Location: Canada
Contact:

Re: Romex wiring between ridgid foam

Postby emtnut » Wed May 17, 2017 4:07 pm

I was talking with Aaron on this ... Even if you glue the foam board on the existing drywall, you would need at least a 3" screw to attach the drywall.So a no-go as far as code.

EMT or MC cable 'could' work ... but I still think you'll have a mold problem brewing !
~~ I'm right on 34 of 100 answers ... That ties me with Babe Ruth :mrgreen: ~~

User avatar
Shannon
Posts: 7645
Joined: Fri Nov 25, 2011 11:58 pm
Location: Canada
Contact:

Re: Romex wiring between ridgid foam

Postby Shannon » Wed May 17, 2017 10:52 pm

If there is an existing poly vapour barrier under the drywall already then you are likely asking for a mold problem. You could remove the existing drywall and vapour barrier and run the wires then add foam and drywall over that.
If you've found our videos or website information helpful, please considering pledging us on Patreon

User avatar
Aaron
Posts: 1089
Joined: Sat Jan 03, 2015 4:03 pm
Location: St. Paul, MN

Re: Romex wiring between ridgid foam

Postby Aaron » Thu May 18, 2017 2:52 pm

That's what I'd recommend. The demo is a pain, but a job done right is a source of pride. You can then use NM cable. Or you could go with batts and a poly vapor barrier instead of the foam.


Return to “Electrical”



Who is online

Users browsing this forum: No registered users and 0 guests