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I want to mount my TV on the wall and just purchase a wall mount for it. I've done this kind of install before, but when I was using my stud finder, it is indicating that one of the studs has AC current. There is an outlet on this stud ~ 1 foot from the floor, but I'm able to detect AC all the way up to the ceiling (and if I go to the second story, I'm able to detect AC all the way up to that ceiling, which is weird, because the third story is an empty attic). Presumably, there is an AC line stapled to the stud vertically.

Is there any way I am able to still use the stud with my wall mount? I'm mounting in a corner so there are only really two studs to use. Am I SOL? Presumably it's a bad idea to drive a 4" lag bolt into the stud, even on center, if there is a powerline stapled to the stud (which itself is an asumption).

This is the wall mount: http://www.monoprice.com/Product?p_id=8586

  • How old is the house? What country are you in? – A. I. Breveleri Dec 3 '15 at 1:49
  • U.S, house is 12 years old. – Joseph Dec 3 '15 at 2:15
  • Oh. I suspected knob-and-tube wiring but your house is much too new for that problem. – A. I. Breveleri Dec 3 '15 at 2:53
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I agree with ppa about the wire running down the stud. Try to determine which side of the stud it is on by slowly moving your detector away until the light goes out. Probe for the stud with a 4d finish nail until you locate the exact ouline of it. Then follow bats advice and carefully drill the stud with a pilot bit for your lag bolt. You may want to be just a hair off center away from the cable but still in the meat of the stud. The pilot bit should be half the diameter of the screw or less. This should guide the screw and keep it from wandering off.

If you take your time and are careful you should be able to avoid the electrical cable in the wall and still get the holding power of the stud. I would not trust #10 screws or drywall anchors for this job.

The best way would be to remove a part of the drywall, attach horizontal blocking between the studs and patch the wall back up. Then you have a really solid installation. But then, this will cost more time and money.

Good luck!

  • Thanks for the reply, @ArchonOSX. Can you elaborate or point me in the right direction on attaching horizontal blocking? I've never opened up a wall before, but this is my first home, I enjoy DIY, and I'd really like to do things the by best practice, so if removing drywall and adding more structure in the wall is the way to go, I'm in! – Joseph Dec 3 '15 at 16:31
  • Here is a link to a Wikipedia page. en.m.wikipedia.org/wiki/Blocking_(construction) Notice the top picture has blocking for kitchen cabinets to be hung. This is also done in bathrooms to attach urinals or wall hung toilets. Or any really heavy objects. With this method you can have several lags holding the TV mount to the wall. Should even hold a 60" plasma. – ArchonOSX Dec 4 '15 at 2:07
  • There are other ways you can accomplish this that wouldn't involve removing drywall and patching. Like a larger piece of wood attached to more studs on the surface. You have to decide what looks best with your decor. I am kind of an overbuilder and I like to have a safety margin for something like this. I guess if you are putting up a 21" monitor it would be different than hanging a 60" screen. Use your better judgement. 😊 – ArchonOSX Dec 4 '15 at 2:18
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Personally I'd be real careful but i'd probably drill that stud. However if you're hesitant play it safe. If you hit the other stud with two lag screws and use two sturdy drywall anchors on the other side, you'll be fine.

I like Snaptoggles.

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you are probably detecting the presence of a live wire stapled to one side or the other of the stud. it runs vertically down to the outlet (and maybe beyond) and up to another device or to its feed line. you should have no issue mounting to the stud, just don't use screws that are too long (1.5" max). remember, if you hit two adjacent studs with 1.5" #10 wood screws, you have a tensile load capacity of about 600 lbs, plenty for a tv. if you are worried about it, just drill a hole and put an inspection camera in, or cut a small hole and feel around inside, then you can see if you can use lags. the mount and tv will cover either approaches residual evidence

  • Why 1.5" max? The wall mount came with hardware, and the lag bolts are > 3.5" long (not all threaded). The TV is on an extended arm, and it's a large TV, so I'm not sure 600lbs would even be enough. – Joseph Dec 3 '15 at 4:02
  • This is the wall mount: monoprice.com/Product?p_id=8586 – Joseph Dec 3 '15 at 4:42
  • here in Canada, the electrical code says that all wires passing through a stud have to be inset into the stud 1.25". by the time you add 1/2" drywall, that gives you 1.75" of depth that the wire is required to be back from the finished drywall face. so if you use a 3.5" lag, you could go right through a wire. you don't need lags that heavy anyways. most TV's barely weigh 40 lbs. even on an arm, its not that much torque. just make sure you hit twos studs, with one screw at the top and one at the bottom, for a total of 4 screws. otherwise, you risk cutting a wire - your initial concern. – personal privacy advocate Dec 3 '15 at 13:42
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    According to this: zillarac.com/Portals/0/Documents/PDF/Screw%20Pull-out.pdf the withdrawal strength of a #10 screw is only 90lbs/inch of thread penetration in a SPF (Southern) stud. If the drywall is 1/2" thick, he would only have 1" of penetration which is only 90 lbs of withdrawal strength. If he doesn't hit the stud in the middle, and the screw fails due to wood splitting, the other screw would take the full 90 lbs. It wouldn't take much for someone to tug on the TV to exceed 90 lb of force in my opinion. I just don't see that two 1.5" lag screws are a good idea. – alfreema Dec 3 '15 at 15:01
  • 26.3in extension on a 9.5" mounting plate means around a 3:1 torque multiplier on the arm. assuming a 50lb tv, this means the upper two mounting screws are loaded at max 75lbs tensile load. under the 90lb you have cited, and not taking into consideration the tensile reinforcement from the reverse moment imparted by the lower 2 mounting screws. so you would be safe just with that. if he is worried about it, he could drill additional holes in the plate and put 2,4,6 more screws as he sees fit. still a better scenario than putting a lag bolt through a wire. electricians bill $100+ /hr – personal privacy advocate Dec 3 '15 at 19:01

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