Electrical wire above open-beam ceiling, below roofing

[SDmark]

Hi,

I live in a 1953 San Diego home on a slab foundation with lovely open-beam 2x8 tongue-and-groove ceilings.

The low-slope roof was rock and tar, then in 1991, they got rid of the rocks and added a hot-mop tar layer. I'm about to have both layers scraped off, add 3" of PolyISO rigid foam insulation, 7/16" plywood as a new base, then a torch-down or possibly TPO roof.

There are two hanging lamps in the kitchen fed directly through the beams that must have wires running above the ceiling and below the roofing, perhaps grooved above the beam. Plus given this once-in-two-decades opportunity, I'm thinking of adding a circuit or two to the master bedroom for possible electric heat and air conditioning.

The question is, what is the right way to run electrical wiring above a ceiling, below roofing, in particular when there will be the extra weight of insulation lying on it? Just lay Romex flat on the ceiling and slap the insulation on top? Groove the wood? Use metal-clad BX?

For the new circuits, if I just want empty conduit for future use, is PVC the best? I'd have to check with the roofer, but maybe it would be possible to groove the bottom of the insulation to accommodate a conduit run.

Thanks for your thoughts,

Mark

 

[WorthFlorida]

You should ask a local electrician and have a electrician do the work. This can vary around the country as what type of wire can be used. He or she would be able to work with the roofers much quicker. While you are at it, the existing wires for the light is probably 2 wire old fabric romex or steel metallic cable with no ground. A good time to rewire those two light fixtures if possible.

 

[Sponsor]

 

[SDmark]

You should ask a local electrician and have a electrician do the work. This can vary around the country as what type of wire can be used. He or she would be able to work with the roofers much quicker. While you are at it, the existing wires for the light is probably 2 wire old fabric romex or steel metallic cable with no ground. A good time to rewire those two light fixtures if possible.

Thanks for the reply. Yes, I want to rewire the existing fixtures if possible. I'm pretty comfortable with electrical work but as you say, a pro will probably work faster. California and San Diego generally follow the NEC so I'm curious if there are code standards for this situation. I may try to call the city inspectors' office as well.

 

[WorthFlorida]

Thanks for the reply. Yes, I want to rewire the existing fixtures if possible. I'm pretty comfortable with electrical work but as you say, a pro will probably work faster. California and San Diego generally follow the NEC so I'm curious if there are code standards for this situation. I may try to call the city inspectors' office as well.

Everyone follows NEC but there are changes every three years and no all municipalities follow new code changes immediately. Since you are in seismic country, California has it own codes to minimize damage from gas and water lines in building structure during a ground movement event. I do not know if there are electrical codes for seismic activity. Hopefully, someone from California may have an answer or as you suggest, call the city inspectors office.

 

[wwhitney]

So the 3" polyiso goes directly on 2x8 T&G? I would think you'd want to groove the foam (or use two layers, gapping the bottom layer) for the wiring method.

I think EMT would be called for, as minimal protection for the 4-1/2" screws that are going to hold the top plywood to the 2x8 T&G. You'd still need the roofers to mark the polyiso and then the plywood with the EMT location so they don't screw through it. If it's just a few runs, you could use RMC for added protection.

I'm not aware of any specific seismic requirement that come in for wiring on a single family residence. Cable wiring methods are inherently more flexible than rigid plumbing or water supply.

Have you considered future rooftop solar and adding either a wiring chase or mount points as part of the reroof?

Cheers, Wayne

 

[SDmark]

@wwhitney Thanks for the reply. Yes, solar electric is planned but so far, vendors have never mentioned wiring chases; I guess they just use conduit above the roof. As for the mount points, the company I'm probably going to use does everything in one day; they won't come out to install stanchions before the roof goes on. Oh and I didn't mention that I'm planning a plumbing re-route in the insulation layer as well. It's dawning on me that with so many moving pieces, I might have been better off looking for a remodeling company than four separate trade specialists...

 

[SDmark]

Talked to a city inspector. For re-wiring lamps to switches, Romex is okay. For possible future expansion, he suggested a 1" EMT conduit.

 

[wwhitney]

For re-wiring lamps to switches, Romex is okay.

Romex is fine as long as the roofers don't put a screw through it. : - )

Cheers, Wayne

 

[WorthFlorida]

@wwhitney .... It's dawning on me that with so many moving pieces, I might have been better off looking for a remodeling company than four separate trade specialists...

As of now you are the GC. That is OK if you are around all day but if you are at work, etc. a hired GC will handle the problems and trades. Yes, it will cost more but most of the time it is worth it. When you are the GC you are constantly chasing problems and no shows. Any contractor bails out and it is you that have to find another trade. Not always easy.