August 14, 2020

How Does a Stud Finder Work? Let’s Find Out Together

How Does a Stud Finder Work

If you need to hang something to a wall (a nice framed picture, a set of shelves, a new tv, etc.), you need to know where the wall studs are, so that you can anchor your object to it and be sure that it is stable. You can probably hang small pictures on the wallboard. But thin wallboard won’t be able to hold the weight of a TV. So you need to locate the studs behind your wall.

Wall studs are usually 2 by 4 or 2 by 6 dimensional lumbers ( which are actually ​1.5″ x 3.5″ and 1.5″ x 5.5″). They are usually placed 12, 16 or 24 inches apart from each other’s center. To find them, the quickest way is to use a stud finder. There are also other methods, but using an appropriate tool is the quickest way to do the job.

Basically, there are two types of stud finders on the market. They work in very different ways. Magnetic stud finders rely on a magnet that is attracted to fasteners (those usually indicate the presence of a wall stud). The more popular ones are electric stud finders. This kind of finder can detect changes in density behind the wallboard. That’s the way it can distinguish a wall stud from wallboard.

That’s the quick answer for you. Now we are going to analyze their functioning in detail in the following paragraphs. We are going to talk about all these different types: magnetic finders, electric finders, wall scanners that use laser technology, and radar scanners. Then, we are going to talk about how to use them, and I will provide you a quick step by step guide.

How Does a Stud Finder Work?

There are three types of stud finders available on the market: magnetic stud detectors, electric stud finders, radar stud finders. Let’s analyze how does each one of these stud finders operate.

How does a Magnetic Stud Detector Work?

magnetic stud finder placed over a wall

These are the first finders that came out in the market many years ago. Their working principle is very simple: they are provided with a magnet (on moving magnetic detectors, a neodymium one). As you know, magnets are attracted to metal. So when you get close to a nail, the detector will hang on the wall. Those nails indicate the presence of a stud.

There are two types of magnetic finders:

  • Stationary magnetic detectors: in this case, the magnet inside the detector is fixed, so it’s up to the user to move the device around the drywall until he feels the magnetic attraction. Then, he needs to move toward that direction until he identifies the fastener’s position. These detectors rely on the user to feel the attraction, which can be quite deceptive if the fasteners are deep into the wall or placed behind thicker material (like plaster).
  • Moving magnetic detectors: in this case, the finder has a “box” inside it, where a magnet (usually a neodymium one) is free to move.  This freedom of movement guarantees more accurate results. The detector doesn’t need the user to move towards the attraction; it’s the magnet itself to move from the rest position in the direction of the metal. Since the neodymium is a strong magnet, these detectors can locate deep nails and work better than stationary detectors when used over plaster.

The only problem is that you don’t actually know if that nail you found is stuck in the middle of the stud; you surely don’t want to miss the center of the stud when hanging heavy objects like a new TV. So it’s probably a good idea to check with a hammer and a small screwdriver if there’s wood behind the drywall around the nail, in order to locate its position on the stud. Alternatively, if you don’t want to ruin your wall, you can check by tapping on on the wall.

Another downside is that a magnetic stud finder might not work on metal mesh lath and plaster. The metal mesh will make nails harder to detect. Furthermore, on a metal mesh it’s harder to identify magnet attraction with stationary detectors or magnet movement with moving detectors.

Most of these problems can be solved with an electric stud finder. Let’s check those out.

How does an Electric Stud Finder Work?

image of a stud finder

This kind of finder is the most common one available. The way they work relates to changes in the dielectric constant of the material they are scanning.

A dielectric constant is a number that describes the way a material reacts when crossed by an electric field. For example, wood has a low dielectric constant, because it’s bad at conducting electricity (in fact, wood is a non-conductor or insulator). The way an electric stud finder works is by measuring this constant while being moved over a wall. It generates an electric field, and based on the electrical capacitance value, it can tell the difference between a wall stud and wallboard. The latter is empty, thus the electric field can move faster, affecting the dielectric value. A lot of models can also locate AC wires, metal, and other materials different than wood (all of them behave differently when crossed by an electric field).

This is the basic functioning of an electric stud finder; now let’s analyze the differences between the 3 types you can get: edge finders, center finders, instant stud finders.

Edge Finders

If you got an edge finder, your tool will detect the edge of the stud (since there’s a change in material density). Then, you need to move it from the other direction to identify the other edge (usually at about 1.5 inches from the first one). After that, you can easily determine the stud’s center. This is the first type of electric finder that came out: it might be inaccurate in finding the edges (there could be up to 1 inch of error). The bumpiness of the wall’s surface can make the tool go out of calibration.

Center Finders

The process I described above to find the stud’s center might be tedious. To avoid that, you should look for a center finder. These stud finders use two sensors at a time, to detect the center on the wood beam automatically. You will need to move the tool only from one direction. When you have found the center of a beam, it’s easy to find the other stud. They are usually placed 16 inches apart (center to center). Most models available are center finders, but it could be a good idea to check before buying, just to be sure.

Instant Stud Finders

instant stud finder

This is another kind of electric finder. These tools come with a lot of sensors (usually, at least 10-15) and don’t need to be moved around to find studs. You don’t even need to calibrate them. You place them over the wall, and they can analyze up to 21 square inches of surface at a time. They will detect studs (center and edges) and areas without studs. They perform well on different materials. The surface bumpiness doesn’t bother these tools like the types presented above. These are more appropriate for professional use. It might be a bit of an overkill if you get one of these for a one time use.


Another type of stud finders available goes under the name of wall scanners.

Wall Scanners

bosch wall scanner

These are a more advanced version of the basic electric stud finder. Their functioning is based on laser technology rather than capacitance detection. As their name suggests, they can find more than just wall studs: they can detect metal objects like pipes, and live wiring. If you need a scanner for wiring, you need to know that this kind of finder can’t detect low voltage wires, such as telephone cables.

Depending on the material you use them on, the detection may go up to 5 inches deep. This value is typical in concrete. They can scan for wood stud up to 1 and a half inches deep. They can locate metal a little deeper, up to 3 and a half inches.

Another good thing about these is that they are self-calibrating tools, so you don’t have to worry about that.

How does a Radar Stud Finder Work?

There’s another kind of stud finder that rely on radar technology (hence the name). This kind of finders are self-calibrated and can detect wood studs, metal objects, pipes, wiring, etc. The depth they can go depends on the material (they can go deeper through steel than wood). Some models can even show movements behind walls (for example, rodents).

This type of finder comes handy if you need to check behind concrete walls, or metal lath and plaster walls (where a common finder might get in trouble).


Now that we got the functioning out of the way, we are going to talk about how to get a stud finder to work.

How to Use a Stud Finder

Now, let’s get down a step by step guide so that you will get the job done quickly:

  1. First thing you need to do is to check the health of your batteries. You always need fresh batteries: you don’t want old ones to distort your results.
  2. Next, the calibration. You need to do this before every scan. Place your stud finder on the wall. Your tool should have a calibrate button: hold it down until the calibration is completed. Your device might make a sound when it’s done. This step depends on the tool you have. You should check the user manual to make sure you do it right.
  3. Place the stud finder on the wall at the height you want to hang your picture/shelf/tv/etc. Make sure the surface is flat and clean (remove traces of dirt and dust if there are any).
  4. Now you are ready to scan. While holding the activation button down (which is usually placed on the side), move the device along the wall slowly. If you shake it accidentally or lift the tool from the wall, you will need to calibrate it again.
  5. At some point, the finder will signal the presence of a stud. It will emit a sound or a light will turn on, or both. It depends on the model. There are 2 possible scenarios now:
    • If you have an edge finder, you just identified a stud’s edge. You will have to move from the other direction to find the other one (after that you can easily spot the beam center);
    • If you have a center finder, then you don’t need to do anything else.
  6. Now, you need to check if what you found it’s really a stud. Go up and down with the stud finder to see if it’s a continuous beam. If you found a pipe, at some point the finder will stop signaling its presence (that means you found a curve). If you have a magnetic finder, you should find other nails at some point.
  7. Another thing to check is the following. Move 12, 16, 24 inches apart from the stud center. That’s the usual distance between studs. If you find something at one of those distances, you can be sure that you just traced two studs. If not, the thing you found before was a pipe or something else.
  8. Now that you are sure you found a wall stud, you can mark it with a pencil and get ready for hammering/drilling.

With some advanced models, these steps are even quicker. As we said before, an instant stud finder doesn’t need a calibration step and will discover multiple studs at once. If you have a common electric stud finder, chances are it comes with different working modes, which are suited to different materials (wires, pipes, and wood stud of course). This makes your life even easier.

How do I find Studs Without a Stud Finder?

Now that we talked about how a stud finder works and the steps to use it, I think it might be a good idea to speak about alternative methods for a second. In this way, you can decide if it’s really worth getting one or if you can get away without it.

  • The first thing you can do is looking for nails in your baseboard. The baseboard is usually nailed directly into wall studs. So if you find a nail, you also find a stud! The other ones will be placed at 12, 16, 24 inches from that. If you discover another nail, you are good to go. If you don’t, knock on the wall at those distances to locate the studs. You will hear a different noise.
  • The light switch is attached to a wall stud on a side. Tap on the drywall to define which side the wall stud is. Again, after finding a stud, check at the usual distances for other studs. Locate them by tapping onto the wall.
  • Starting at the corner of the wall, measure it with a tape and see if its length is divisible by 12, 16 or 24. After that, tap at the proper distance from the corner to see if there’s a stud there. To identify the edges of the stud, hammer a small nail into the wall and check if you can find the stud.
  • Use a flashlight. Place it parallel to the wall and start looking for dimples in the drywall. Those are probably the places where the wallboard is attached to the studs. Don’t rely on this too much. It’s probably better to also tap on the wall after this to check for the stud or check with a hammer and a small nail/screwdriver.

As you can see, there’s a lot of trial and error involved. If you want to do the job as quickly as possible, it’s probably better to get a stud finder.

Conclusion

As we saw in this article, a stud finder functioning is very different when considering a magnet stud detector or an electric stud finder. The first type relies on finding metal objects (i.e. nails inside the studs), the second one can actually detect different densities and therefore studs. The latter method is more precise and requires much less time. With a magnetic finder, you may found yourself looking for a nail in the wall for a long time. If you need to choose between them, you should always go for an electric stud finder.

If you are short on time or money, you can try with one of the methods I talked about in the paragraph above. You can always get a finder later if you can’t locate the studs.

There’s one thing you need to keep in mind: when looking for wall studs, make sure to always double-check what you find. You don’t want to hammer a nail into a pipe, or even worse, into some AC wires. Always check for more studs at the distances I mentioned earlier (12, 16 or 24 inches). If you remember to do this, you will be fine.