How do you avoid hitting a live wire when nailing or drilling into your drywall?

April 23, 2008 5:49 PM

How do you avoid hitting a live wire when nailing or drilling into your drywall?

From what I understand wires run along studs but sometimes also through studs. There are supposed to be studfinders with live wire detectors but I don't know how reliable they are.

posted by GleepGlop to home & garden (13 comments total)

You could turn off the breaker for that circuit and run an extension cord from elsewhere to power the drill. This assumes you're more concerned with the "live" part than the "wire" part.
posted by Inspector.Gadget at 6:20 PM on April 23

Judging by customer reviews, this gizmo seems to do the trick. (Other stud finders get "worthless" ratings, "beeps randomly", etc. I gave up on my own stud finder and use my knuckles to find the stud, but I may have to try this Irwin.)
posted by beagle at 6:21 PM on April 23

Inspector.Gadget: the problem is, you really have no idea what circuit is running through the wall in any particular place, so how do you know what to turn off? In theory, if you hit the wire with a properly grounded tool, you'll survive. But now you've damaged the wire, which is not a Good Thing. However, truth be told, this is not a big risk. Without using any wire finding tool, I've done plenty of nailing and drilling and only once in 40 years have I hit a wire. Still, it might be worth investing in a wire detector.
posted by beagle at 6:26 PM on April 23

The live wire detection function of a stud finder with that built in is going to be more reliable than the stud detection function, simply because there's an actual electrical disturbance there to detect, rather than just a subtle change in dielectric constant.

But the main thing is common sense. Putting live wires in existing walls is a pain in the arse, and new walls are generally built so as not to electrocute future handypeople. So, most of the live wires in your walls will be coming straight down the shortest path from the ceiling (where most of the lighting distribution wires run) to the light switches, or from the subfloor (where most of the power distribution wires go) to the power outlets. If you avoid nailing things to your walls near the visible electric fittings, you should be pretty safe.
posted by flabdablet at 6:28 PM on April 23

Most modern digital stud finders will identify unarmoured wires. Make sure you read the directions, or watch the DVd that comes with these. most people complain about them because they haven't taken the time to learn to use them properly

Make sure you don't use nails and screws longer than you need to.

if your house was built in the last 10 years, it should have some safeguards, like steel plates on studs in front of wires, to help prevent this

it does happen, not often
posted by Mr_Chips at 6:29 PM on April 23

Wires should be stapled to the middle ( about 2' in from the sheet rock face) of the stud, or run through a hole drilled in the same place. If for some reason the wire has been run closer to the wall, a metal plate should have been nailed over it . This is Code and standard practice but sometimes things are not built the way they ought to be. I'm unable to add to the information about the wire finders. Use short nails and/or grounded and insulated tools.
posted by Hobgoblin at 7:01 PM on April 23

Here (Australia), wires are never run through studs, only down between them, for exactly this reason. A stud finder should have no problem finding any wires and you can also get some idea of where wires are likely to be by mentally tracking back from wall fittings etc. If you can get into the ceiling space (or underfloor space if there is one), you can gather a lot of information about where wires are run, too.

Grounded tools, ELCBs or pretty much anything else won't help you much if you bridge across active and neutral with a nail or screw and the first you hear of it is likely to be when you touch the nail/screw itself and wake up dead. Electricity is dangerous, so be careful, but it's pretty safe if you take simple precautions.
posted by dg at 8:08 PM on April 23

2 people. One holds the stud/wire finder, the other flips breakers until the finder stops flashing. Drill away!
posted by wemayfreeze at 12:31 AM on April 24

Honestly, the chances of your nicking any wires is extremely remote. I've never heard of anyone doing so.

If you pay attention to your drilling, you can easily stop just as the drill bit breaks through. You can also wrap a bit of tape around the bit about 1/2" back from the tip (or however thick your drywall is). This will give you a visual indication of when to stop drilling.
posted by Thorzdad at 4:38 AM on April 24

Years ago, I was working with my dad when he drilled through a power cable - a sheet of flame, a bang, and he's left with a shocked expression and lots of shattered metal. And he's an electrician, so it does happen, even to those who should know better.

The answer is turn the power off at the circuit breaker, use a metal detector to avoid metal (even if you think the power's off), and use a battery-powered drill. My dad works with the site power off whenever possible, although he also carries a "real" drill for heavier tasks.
posted by Leon at 5:16 AM on April 24

If your building has a slab-on-grade foundation instead of a crawlspace, then the power wires will probably be running through the wall studs to reach outlets; but then they'll pretty much be run at outlet height, about 18" above the floor. Areas like kitchens and laundry rooms where outlets are located above the countertops would be exceptions to that, but most people generally don't need to nail into walls that low. As others have said, nail guards are required over stud penetrations in new construction, but that doesn't necessarily mean they'll actually be there.
posted by LionIndex at 8:15 AM on April 24

Hmm thanks, I'm going to look into a stud / wire finder... They're cheap!
posted by GleepGlop at 3:22 PM on April 24

Wow I wish I had seen this thread sooner. This is coming really late, but I'll toss this in here anyway. As someone who hangs drywall for a living I can tell you the chances of hitting a wire in your wall are slim to none. If for some reason the wire is run close enough for a nail or screw to hit it, it would have to be covered by a metal plate in order to pass an electrical inspection. But most wires are run either down the side of the stud or an inch or more into the center of the stud, allowing for a inch and a quarter screw or nail to be driven without coming close to hitting the wire. If the drywall is half inch (standard) that gives you 1/4 of protection from any problems involving nails or screws. Most wire are run from the top plate (near the ceiling) to the box or through the bottom plate (near the floor) the long and short of it is don't worry about hitting wires unless you use a huge nail or screw. You could also check to find out what kind of electrical codes are enforced in your area, because it's likely any wires that might be vulnerable are required to be covered by a metal plate
posted by nola at 7:40 PM on August 4