How to handle wiring at intersections with continuous drywall?
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| Posted in Mechanicals on
Continuous drywall, where a gap is left between exterior walls and intersecting interior walls so that drywall sheets on exterior walls can be slid through, is recommended in a couple of articles here on GBA for a more airtight assembly, and it seems like an excellent idea, but what does one do with wiring that runs from the exterior wall into the interior wall? Wiring that crosses the gap would prevent the drywall from sliding through. Is the only solution to run the wire up through the top plate and then back down so that you go over the gap instead of across it?
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Replies
Yup, down from the attic or up form the basement.
I find the 2x6 backing behind a 2x4 wall stud a much simpler install for air tight drywall. The drywall can mount onto this 2x6 and give you air barrier continuity across the interior wall intersection.
Jeff,
One of several reasons I'm not convinced it's a good idea. Two others are:
- Interior petitions are a good place to end drywall runs. Otherwise they probably end up in the field, meaning another butt joint on the wall.
- There is no ceiling drywall behind the interior partition, meaning you end up with a gap above the top wall board there. That and not being able to tape the seams behind the stud means it's unlikely to be more air-tight than a conventional setup.
Residential wiring is mostly run across the attic and down these days. I prefer going up from the basement myself, but things are what they are. The goal is to avoid having to drill through a bazillion studs to run a horizontal cable, thus saving time. If you run everything above the ceiling or under the floor in this way, the wall details don't really matter since you're not crossing studs horizontally very often.
I like Akos' suggestion with the 2x6 though -- that's clever. That would let you run the wiring more normally through the studs if you want to, just remember to seal the hole to preserve the integrity of your air barrier.
Bill
Bill,
I haven't noticed much change in how electricians run wire. Around here anyway, the attic drops are fairly few compered to the horizontal runs - which from an air-sealing p0int of view is better. I'd rather avoid as many holes in the top plates as I can.
Around here, horizontal runs are generally avoided by the crews. They prefer to go down or up (usually up), then staple across to save on drilling holes in studs. There are still horizontal runs for recepacles, but not as many as you'd think even for that.
The downside is that the wire runs get a LOT longer when everything goes up to the attic and back down, and that means more voltage drop. Voltage drop doesn't help anything to work better, and if you look at it from a green perspective, it's extra system losses too -- so less efficient. I am not a fan of wiring this way. There are codes about voltage drop, but inspectors rarely check for that.
Luckily for me, I do mostly commercial work where we can stretch our MC cable horizontally above drop ceilings and make all the runs as short as possible :-) Ha. I often spec EMT conduit for things just to keep stuff neat. The older electricians like to make their installs clean, but a lot of the newer crews are all about speed, which often makes for a mess above the ceiling.
bill
Thank you, Akos, Malcolm, and Bill. I'm convinced the continuous drywall isn't worth it. I figure it would use an extra 12' or so of wire every time I have to go up and over, and your points about the other disadvantages, Malcolm, are persuasive. I am going through the ceiling for most of the initial runs from the main panel.
I avoided most of the need for drilling studs by creating a wiring chase between the two halves of my double-stud wall, which are separated by an inch of EPS foam board with a small gap for the cables. For the drilling I have to do, I got a set of Irwin Speedbor bits that take around 3-4 seconds to drill through a 2x4 and produce very little dust, unlike the much slower spade bit I tried first.
Those bits are nice. I like the Greenlee "Nail Eater" bits too, which are similar. These bits can grab though, so be careful -- especially in harder wood or around knots. Also be careful if you're near any masonry -- it takes suprisingly little damage to the cutting edge of these kind of drill bits to make the drill bit so bad it becomes junk. I've damaged several bits by nicking the top of a foundation wall just a tiny bit while drilling in nearby joists.
Bill