A stud finder is good for, well, finding studs you can’t see. Knowing where those are is crucial so you can be sure to screw into them instead of just the drywall when you’re hanging something heavy, like a mirror or a mount for, say, a flat-screen TV. But some stud finders have other features, too, like deep scanning and AC wire detection. That doesn’t mean they always do what they’re supposed to. There’s a lot going on in walls, and it can be hard, despite advances in tech, for any device to parse it all and determine what’s a pipe and what’s a wire from outside of the wall. To test all the features, we put a selection of stud finders through their paces on a wall of our own making, as well as walls in existing homes.
How We Tested
For our test, we built a four-by-eight-foot wall out of common materials: wood and metal studs; drywall; copper, black, pex, and PVC pipe; and nonmetallic sheathed cable. Then we scanned the wall with each of the stud finders. All functioned as expected when it came to detecting the studs, but we quickly found that a number of them designed to pick up the location of live AC wiring simply didn’t. We checked with product engineers and found that steel studs, metal pipe, and ductwork could impair live-wire detection. So we went back to our test wall, removed the steel studs and metal pipes, and built a second four-by-four-foot wall to test only the steel studs. Again, stud detection went as expected, but the devices did only a slightly better job of finding the live wires. A couple did, however, manage better than the others. We also took the stud finders to two homes—one a mid-1800s house with lath and plaster, and the other a 1970s tract house—for real-world testing.
What You Need to Know About Your Walls
Most studs are spaced at 16-inch intervals—find one, and the next stud should be about that same distance in either direction. Changes in spacing usually happen near the ends of walls or near doors and windows. If your stud finder seems to be picking up things between the studs, it could be detecting metal or plastic plumbing components, electrical boxes or wiring, or metal ductwork. Electrical wires usually run vertically on the side of a stud and sometimes horizontally between outlets. Keep this in mind, and if there are light fixtures, switches, and outlets on a wall, you can make an educated guess as to where the wires might be. And pay attention to where the kitchen and bathrooms are. Water-supply and waste pipes for the second floor are often found in walls on the first floor, below sinks, tubs, or showers. Pro tip: If your basement is unfinished, you can go down there to see on the ceiling where exactly the pipes go up.
Don’t touch the wall with either hand while you’re using a stud finder—this can alter its readings.
Some tools need to calibrate before scanning, so start away from switches, outlets, or light fixtures.
Apply some painter’s tape over the area you want to scan. It’ll give you a surface on which to mark your findings without having to write on the wall.
When you detect studs, objects, or live wires, mark them.
And where you detect a stud specifically, scan above and below that point to make sure it continues to the floor or ceiling. Other readings, not at regular intervals, could be wiring, plumbing, or ductwork.
Freshly painted walls may be difficult to scan for up to two to three weeks, due to the moisture in the paint.
The Bottom Line
Stud finders have their jobs cut out for them, given the many variables in wall materials and construction. While you may get definitive results in one case, you may be left scratching your head in another. Take everything with a grain of salt, and use the stud finder in conjunction with the placement of electrical and plumbing fixtures to figure things out. Be careful about assumptions, err on the side of caution, and take your time.
Bosch GMS 120
Bosch’s GMS 120 is much more than a stud finder (though it did locate the centers to within an eighth of an inch). It can also detect live AC wiring, metal objects, plastic pipes that are filled with water, and even rebar in concrete. The Bosch unit has audible tones, an illuminated ring around the sensor area, and an LCD screen—and all three work in concert, guiding you to what you’re scanning for. The ring turns red when over a stud, while the screen provides live-wire alerts and displays a bull’s-eye to indicate the stud’s center. Though the GMS didn’t find wiring in our wall, it did pick it up fairly accurately in the test houses.
―WIDEST SCAN AREA―
Franklin Sensors ProSensor T13
With 13 sensors spread out over its seven-inch surface, the ProSensor T13 scanned deeply to accurately locate studs. When we encountered one, the LEDs over it lit up to show its full width. The T13 even proved wide enough to show doubled-up studs around door frames and windows. We found it simple and easy to use, and it reliably detected wood and metal studs under three-quarter-inch-thick drywall. While this unit isn’t designed to locate pipes or wiring, we did get a blink of one LED when we ran it over copper piping.
For finding studs, things don’t get much simpler than The StudBuddy magnetic stud finder. Using it, we effortlessly located nails, screws, or metal studs by sliding it in an “S” pattern, back and forth on a wall. Two strong neodymium magnets will cause the StudBuddy to snap to ferrous fasteners or studs when we got within about three-quarters of an inch of them. Sliding it up or down quickly confirmed additional hits, and the location and direction of studs. We found it worked even better on metal studs because fewer confirmation “hits” were required. The StudBuddy may also locate other ferrous metals in the wall, like ductwork or electrical boxes—so scanning to confirm stud orientation is important.
―EASIEST TO USE―
DeWalt DW0150 Stud Finder
DeWalt’s DW0150 was consistent in finding stud centers, locating both wood and metal equally well through both half-inch and three-quarter-inch drywall. An alert in the form of an LED arrow pointed toward the studs, and we found that traveling over the stud and then back until the DW0150 picked up the center was nearly 100 percent accurate. (We’ll give DeWalt kudos, too, for including a window in the center, which made marking stud centers with a pencil easy.) The device also detects AC wiring—it was reliable through a half inch of drywall but only intermittent under the three-quarter-inch variety.
Zircon Superscan K3
Zircon’s Superscan K3 is a specialized wall scanner, designed specifically to pinpoint the centers of wood studs. Additionally, it can locate other metallic and non-metallic objects in walls. In our testing, the K3 was very reliable detecting studs, indicating center by projecting a red arrow on the wall. In deep scan mode we picked up everything we have in our test wall, including studs, black pipe, copper pipe, polyethylene pipe, and NM-B electrical wire. When we passed over live electrical wires, the screen turned red and displayed an icon indicating the wires were live. In dedicated metal scan mode, we found it easy to differentiate between metal plumbing pipes and wood studs. If metal studs were present, it was a little trickier, but using the signal strength indicator helped sort out things that were close—the stud—versus things farther inside the wall, like pipes. We noted that, occasionally, the K3 would indicate a wider “hit” than the actual object detected. While not perfect, it is much better than not detecting an object—it reliably steered us away from potential hazards.
Stanley S50 Edge-Detect
If you just want to locate a stud, Stanley’s basic S50 is all you need. It was designed to locate the edges of wood or metal studs. Just press the button and glide the S50 slowly along the wall, keeping an eye on the indicator. When it lights up, you’re at the edge of one. It’ll stay on until you pass the other side, so once you do, slide the unit back over the stud to confirm and mark the edges, then measure halfway between them to find the center. In our testing, the tool consistently found studs under half-inch drywall. Detecting the edges through three-quarter-inch drywall was slightly less accurate, though.
Craftsman CMHT77623 Stud Finder
Craftsman’s center-finding unit has LEDs to indicate scan status and guide you to the center of the stud—orange ones light up when you’re over the stud, and red ones indicate when you hit the center. Scanning slowly in one direction, past the center and then back, got us accurate results over half- and three-quarter-inch drywall. The AC detection mode was somewhat vague, indicating an area three- to four-inches wide when it picked up wiring. But repeated passes allowed us to determine the wiring’s path. In standard scan mode, the Craftsman located some copper pipe, which was odd, but the pipe was too narrow to be a stud and the device never registered a center. Similarly, it detected black pipe in metal mode. (Note that although it located the pipes, the stud finder couldn’t, nor was it designed to, identify them as such.) Still, these readings can help you identify other objects in the wall you may want to be careful around.
―BEST FULL-WIDTH SCANNER―
Ryobi LED Whole Stud Detector
Ryobi’s Whole Stud Detector lives up to its name. When it finds a stud in the wall, it shows the width by illuminating some of its seven LEDs: Whichever are over the stud will turn on, and whichever aren’t will remain off. And it didn’t matter if the studs were wood or metal, this Ryobi found them both under half- and three-quarter-inch drywall. It also picked up pipes but couldn’t tell us what they were made of. (Though in fairness, the pipes were four inches apart, a sure indication they weren’t studs.) We detected live AC wires in five-inch swaths and followed their paths—so we knew where they were, although not precisely.
Zircon Metalliscanner m40
Zircon’s Metalliscanner m40 is quite basically a metal detector. It is capable of scanning for ferrous metals up to four inches deep, and non-ferrous metals two inches deep. In testing we found it very easy to accurately pinpoint drywall screws, due to the very small contact area on the tool face. By watching the LED signal strength indicator go up and down, we could stop at the maximum reading, directly over the fastener. We were also able to locate copper electrical wires and copper plumbing within about two inches of the wall surface. While not part of our regular testing, we also used the Metalliscanner m40 to locate studs in plaster walls—via the nails in the lathe, as well as rebar in concrete. The Metalliscanner m40 is a powerful metal detector, however it won’t help find non-metallic plumbing or indicate if electrical wires are live.
―MOST SCAN MODES―
VIVreal Stud Sensor
The VIVreal Stud Sensor was selected based on its high ratings on Amazon, the only place we found it available. It features four scan modes: three for specific objects (wood, metal, live AC wiring) and one for deep scanning. Though its edge finding was lackluster, it accurately detected the centers of studs, with a “center” notification displaying on the screen to let us know we’d reached it. We found this to be consistent in wood and metal scan modes, through both half-inch- and three-quarter-inch-thick drywall. In metal scan mode, the Stud Sensor detected copper and black pipe, just without a center indication, showing that they weren’t studs and not in contact with the drywall. In deep scan mode, the VIVreal detected copper pipe, though it was off by about three inches. Live AC wire detection was unreliable, too, and the finder couldn’t determine wire paths in our test wall. However, it did detect live wires reasonably well in both of our test homes.
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