What's behind my wall? Is it safe to mount a TV?

Question

My house is located in Washington state and is wired with ethernet and coaxial cable to several rooms. I am hoping to mount my TV on an exterior wall. I've been looking for studs using a Zircon MultiScanner A200 stud finder, which includes a built-in live AC wire detector. There do appear to be some consistent studs with 16" spacing, but the other results I'm seeing are a bit confusing:

The dark gray dots indicate locations where the "StudScan" mode detected the center of a stud. The yellow dots indicate places where it displayed the symbol to indicate the presence of a live AC wire.

The results in some locations were very inconsistent, which I've indicated with ovals in the photo. Particularly the live wire warnings wouldn't always reappear when I moved the stud finder off (still against the wall) and back on to the same location, so I'm not confident in the accuracy of any of the yellow dots. (I also saw brief flashes of the live wire symbol in some locations that aren't pictured — these are just the ones where I saw slightly more consistent readings.) It seems like there is more empty space between the centermost two studs, which are likely the ones I would want to use, but there still might be some wires there.

The other side of the wall looks like this, with our main electrical breaker and gas meter. There is a breaker box inside the house, one floor up on the opposite side from the TV.

How safe or unsafe might it be to drill 3.5" or so into the studs I found? Why does there seem to be one stud about halfway between the usual 16" spacing? Would the electrical wires, ethernet/coax cables, etc. be located near the sides of the studs, between the studs, in front of the studs, or what?

Answer 1

Skip the problem entirely.

You are probably going to want to put a hole in wall behind the TV. That hole will be where you run your cables through, or possibly put in an outlet. Since you know that is going to happen, forget about drilling and avoiding wires right now, and MAKE THE HOLE FIRST! Then you can see what's back there.

Mounts usually have holes in them sized to allow outlets to be placed inside the mount footprint. Take advantage of that, mock up where the mount will be, cut the hole for your outlet/cables, locate your studs and wires, and then drill with certainty!

Answer 2

I wonder if the cluster of 6 yellow dots on the left could be leakage from the meter box and its cables. I wonder why there are no yellow dots leading clearly to the known outlet .. .although those could simply be coming straight up from the basement, and you didn't look there. I wonder if the cable detection is so unreliable you should ignore it.

Here's what I would do: Ignore the extra stud. Doesn't matter. Use two of the clearly identified studs, the middle two. To be safe, use 1-3/4" screws if you have 1/2" drywall, or 2" if you have 5/8. (Assuming you have a single layer of drywall directly on studs ... for the hundred other possibilities you can adapt the logic)

Don't use a single-stud TV mount. Buy a good mount, use four screws in two studs.

Answer 3

It is standard to place studs at 16 inches, but does not mean an extra stud cannot be placed differently for some reason. Extra piece to place screws/nails or support for something.

Electrical cables are usually placed on the sides of the studs when building, but after building can be closer to to centre of the stud bays.

Two inches in from the drywall surface is usually consider safe to prevent drilling into wires, 3 and 1/2 inches is usually overkill.

Answer 4

I would suggest finding the live wire that feeds the receptacle behind the TV.

if you can find the path possibly a horizontal path at the height or a little above the receptacle you probably will find this at that height. This would provide the only likely hots if there is a horizontal run and this would be the only places that were drilled others would be stapled to the side and normally safe to drill deeper.

some of the positives may be from the service feeder (yes in pipe can still create a field) then it is relatively safe as traveling at an angle is not a standard method for most electricians, the safe depth is 1-1/4 +1/2” or 1-3/4” if there is wiring there 1-1/4 is the required code set back from the face of the stud +1/2” drywall /Sheetrock being the common thickness.