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I'm getting ready to mount a flatscreen TV on our living room wall and would like to route various cables through it (e.g. surround sound speakers, HDMI, etc). I appreciate the AWESOME tips here, but I think I'm missing something important: How can I find out what's in the wall without causing damage or creating too much of a mess?

My concern is that there may be electrical wiring, plumbing, insulation, or dead rodents (kidding) in there.

Our house is about 50 years old and the wall is shared with the kitchen on the other side but there's no sink attached to that wall. Wall material is drywall.

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7 Answers 7

up vote 10 down vote accepted

A stud finder is completely non-intrusive and will give you a good idea of how the wall is built. Run it horizontally back and forth at several different heights to map where the studs are, then run it vertically within your newly-found stud cavities to see if there's any lumber going between the studs.

You can guess at where the wiring might be by looking at electrical fixtures on either side of the wall. If you can, look at the base of the wall from your basement or crawlspace, and at the top from the attic, which might give you some more information. If the builder installed protective plates where the wires feed through the studs, a magnet will let you know. Some stud finders also include a detector for AC that will help you trace any electric wiring in the wall, or you can get a standalone detector.

In my experience, plumbing is usually run directly to where it's needed, so if there are no pipes in the basement/crawlspace, or vents going up to the attic and out your roof, there are probably no pipes in the wall either.

Once you've found a safe spot to open the wall, a boroscope or inspection mirror will let you look inside the cavity. A boroscope will be less intrusive, but an inspection mirror is a lot cheaper.

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3  
My stud finder has the AC detecting feature. It usually tells me there's a live wire behind every square inch of the wall. Okay, it's not that bad, but it really isn't that helpful. Maybe it's the $10 price tag on the stud finder. –  Doresoom Dec 2 '10 at 14:25
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Maybe it's just my terrible luck, but I've always had nothing but problems with stud finders. What I found recently which really worked for me was using magnets to find the nails used to fix the drywall to the studs. Run a magnet up and down the wall and when it sticks, odds are you've found a stud. After that, verify with a stud seeker or with a finishing nail, then hammer away. Any recommendations on a good reliable stud detector? –  Naftuli Tzvi Kay Oct 16 '12 at 15:38
    
They actually make magnetic stud finders that release a magnet as you sweep it past a nail/screw in the drywall. –  Doresoom Jan 16 at 22:40

When I've done such cable running jobs my usual approach was to use a stud detector, or even a neodymium magnet, to find the studs in the wall which will therefore give me an idea of position of the vertical, and horizontal, wooden supports.

The next step I took was to head to the floor above to access the gap between the cavity wall from above and do some rough measurements and an inspection of where I'm going to run the cable down. If everything looks clear enough to run a cable that's all you need to do. Armed with this info I slot a sturdy length of plastic down the cavity wall at the position I want to run the cables, an old curtain runner is ideal since it is strong and flexible enough to go round small corners.

Back downstairs if you've measured up the position of your hole correctly you should be able to spot your length of plastic, if you can pull it through the hole then you're nearly there if not you're going to have reverse the operation and retrieve the plastic from the floor above and shove it through your hole and up through the cavity wall. Then you can attach your wiring to the length of plastic using some strong tape and pull it through from above, this method also works a treat for running cables under floorboards.

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A simple home made metal detector.all you need- 5 minutes free,some tape,a calculator and an AM Radio

http://www.wikihow.com/Make-a-Homemade-Metal-Detector OR http://www.instructables.com/id/HomeMade-Metal-Detector/

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Answers that consist of only links, are very susceptible to link rot. Please summarize the information contained in the link, so if the link dies this will still be a useful answer. –  Tester101 Oct 5 '12 at 17:00

My approach has been:

  • Drop baseboards.
  • Knock out a small hole behind the baseboard.
  • Stick my iPhone in.
  • Snap a bunch of photos with the flash on.
  • If the photos aren't working well enough/providing enough coverage, I'll record a video with the flash on.

This has been tremendously useful in working out where cables are and where they've been stapled to the studs.

An iPhone-sized hole could also be knocked out higher on the wall. Mid-wall gives you good visibility to the rest of the stud cavity. And patching is just throw a piece of tape over the small hole and mud away.

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On the baseboard tip, cut the hole at least 1 3/4" above the floor to be above the sill (horizontal framing at floor level). –  bib Oct 2 '12 at 17:46
    
@bib Oops, I took for granted you could see the sill. My wallboard/plaster (1" thick total) ends at a flush 1x1 nailed to the studs just above the sill plate, so I can see the sill plate everywhere. –  Jeremy W. Sherman Oct 2 '12 at 18:20

Try a borescope

Borescope recommendations (features)

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If you have an attic or a basement get over/under the wall and look. The sill plate and the cap may hide some things, but there will inevitably be something poking through nearby.

You've already thought of plumbing, are there any outlets or vents on that wall? What about cold air return grates?

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There are some electronic inspection cameras on the market. Might be an excuse to buy one.

You would have to make one or more small holes to insert the camera.

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