How To: Find Studs in a Plaster Wall

By Scott Sidler • September 2, 2013

how to find studs in a plaster wallIf you own an old house with plaster and lath walls, you may have discovered how utterly useless a stud finder can be. Most smaller items can be hung pretty securely anywhere on the wall by screwing into the wood lath, but for heavy things that weight more than 10-15 lbs, like large mirrors and TVs, you’ll need to learn how to find studs in a plaster wall.

Don’t waste your money on that stud finder. Try these simple and time tested tricks to find studs in a plaster wall the next time you need to hang something in your old house. The third trick is my personal favorite because it never fails!

#1 Find an Electrical Box

Electrical boxes for outlets and light switches are supposed to be attached to studs. Though there may be an occasional free floating box in an old home, you have an excellent chance of finding a stud on one side of the box. To see which side the stud is on, take the switch plate cover off and take a peak inside. Either turn the breaker off, or be careful not to touch any wires before attempting this or you can get a nasty shock.

Once you find the stud, you can measure off 16″ to find the next one most times. Most houses built in the last 100 years were framed 16″ O.C. (on center) and some were framed 24″ O.C. although many old houses may have unusual stud spacing so this method may not work for everyone.

#2 Knock on the Wall

This one may seem old fashioned, but gently knocking your hand along the wall and listening for differences is a pretty accurate technique to find studs. When you knock on wall sections without a stud, you will hear more resonance from the hollow space behind. Once your knuckle hits the spots where a stud is located, the sound will change to more of a dull thud. Move along the wall and look for a pattern to show itself, and you’ll slowly be able to see your stud spacing.

#3 Use a Magnet

How to find studs in plaster wall
The magnet trick!

This is my favorite method and the reason is simple. It works every time! Grab the strongest magnet you have and tie a piece of dental floss or string around it. Dangle the magnet against the wall and slowly move it horizontally across the wall. You have to go slow. Every so often, the magnet will stick to the wall a bit on the stud location. It has to be a strong magnet for this to work, so those floppy pizza magnets won’t cut it.

The reason this works is because the wood lath is nailed to the studs, and the magnet is attracted to those nails. Keep in mind there are some spaces between lath vertically so if you’re not having much luck try moving the magnet up or down a bit so that it is over top one of the hidden nails.

Update: Since I first wrote this post we have begun offering a totally cool new product called StudPop which takes the magnet trick to the next level. This simple stud finder is a powerful magnet that pops into place when a stud fastener is detected. Just like my magnet trick, but a bit more refined than tying dental floss around a magnet. Check it out here!

#4 Use a Metal Detector

If you happen to have a small metal detector, you can use this along the same premise as the magnet technique. Beware that depending on the sensitivity of your metal detector you may pick up old wiring, cast iron plumbing, or other things hiding in the wall. Unlike the magnets which aren’t strong enough to be attracted to a pipe that is a couple inches recessed into the wall the metal detector may give you false readings.

So, there you have it. No more fumbling with expensive stud finders that give you all kinds of weird readings. Other than the metal detector, these techniques have been used for decades to find studs in plaster walls. The best part? They cost you almost nothing. And saving money is an important thing with all the other repairs lingering in an old house.

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65 thoughts on “How To: Find Studs in a Plaster Wall”

  1. I used a neodymium magnet on my plaster/lath walls, and nothing! I want to hang a tv up in the corner of the room, and I need something that works due to my over optimistic wife, who doesn’t want anything happening to the walls. I need to create more room in my office, so I was going to mount the tv, then build a desk that folds up on the wall. My house is about 65 years old. Thank you!

  2. Anyone have a suggestion on using the magnet & dental floss method to find my ceiling joists? I want to hang two very heavy leaded glass transoms from my ceiling but how to find the joists? My house is a 1906 craftsman bungalow. I know they didn’t use the standard 16” o.c. In early construction so I can’t just measure off.

    1. locate where you want the glass to be,
      somewhere in that defined region drill a one or two inch exploratory hole and look with a mirror.
      you can measure a distance from an edge of the hole by making an “L” shaped wire and cutting down a leg until it just touches an edge of your found stud. good luck

    2. Since you are trying to find the screws holding your drywall (or plaster and lath) into the ceiling there is obviously no need for the dental floss But you should still be able to make use of a STRONG small magnet by holding it up against the ceiling with your fingers and moving it very very slowly until you find a drywall screw. It will be more awkward than dangling it on a piece of string but the principle is the same and if you take your time you should be able to discern where the magnet is attracted to.
      Remember, you are not looking for your joists directly with your magnet , you are looking for the screws that hold everything into them. First find one screw (mark it with a pencil) and then take your time to find the next screw, then keep going (and marking) until you figure out how the overlying wall is nailed (or screwed) into the joists.
      Once you think you’ve found the joists use a drill to drill tiny pilot holes to make sure that it is indeed the joists that you’ve found (the drill gets resistance all the way through into wood) then use lag bolts to anchor what you need into the joists.

  3. I save the little magnets from gift boxes & things like that that have magnetic closures, they are tiny rare-earth magnets! A couple of the in a stack worked great.

  4. 1850s house, lathe. Trying to hang a large shelf. Magnet on string finds but 4 nails on entire wall; two about 5′ off floor 21″ apart and another two about 4′ off floor about 21″ apart. If they are nailed into the same stud it is a 4″x 4″x 10′, or they are somehow anchored to the sides of the studs. Nothing else found on the whole wall, I think all the wiring was added by running wires down inside the walls into the basement. The outlets are screwed into the baseboard and switches are just screwed into holes cut in the lathe. Seem to be no nails at all in the baseboard, at least ferrous ones. Standard stud finder tells me the whole wall is a stud and hot with wiring. I assume there are old gas lines in there too as I had to unscrew some to put in ceiling fans. Seems like there should be nails in each lathe along the entire stud, not just 4 of them holding all the lathe and I never heard of 21″ on studs and there should be more than 2 studs on a 14′ long wall. Any thoughts?

  5. Zircon’s i360 studfinder has a METAL detector setting along with STUD and DEEP SCAN. Sliding the unit back and forth (going about a couple inches up or down with each pass) quickly started showing the locations of the support stud nailed points were. A couple of refining sweeps helped find the stud boarders, while sweeping vetically up & down confirmed more nailed locations along the stud.

  6. Stanley magnetic stud finder! It just has a little peg on a pivot. When you cross over a nail it stands straight out. Super simple and works great. Plus… like 2 bucks

  7. I tried the magnet trick on my walls, but it stuck everywhere. Someone else said they have expanded metal mesh, and they had a similar result. Do you think that’s what is happening with my walls as well? If so, do you have any suggestions?


  8. Thank You. We just bought an old house and I’m putting a second handrail in the stairway. I missed the stud with the electronic sensor. I have just the magnet!

    1. So glad our post was helpful for you! Good luck with your old house restoration and thank you for commenting on our post! We’d love to be kept in the loop on your projects. Feel free to write us any time!

      -Alyssa (Designer at The Craftsman Blog)

  9. Bought a stud finder, only to find out inside the package that it will not work on plaster walls! Checked out the outlet box, only to find out that it was cut directly into the lath and screwed on the top and bottom of the electric box! (who does that!!!!????). Knocking on my wall just hurt my tiny little knuckles! So, I am going to try the magnet thing now! If I don’t have a powerful enough magnet . . . I will be purchasing a STUD POP!!! I love all these helpful comments and am grateful for Scott and his wisdom! 1900 home means “The Craftsman Blog with Scott Sidler” is my new best friend!

    1. Hi Andrea,

      Did the magnet trick end up working for you? If not, I hope you were able to order a Stud Pop and I hope it changed your life! (Not to be dramatic, but really haha)

      Be sure to subscribe to the blog (and our YouTube channel! ) to get the latest articles directly to your inbox. You’re going to be needing that with your lovely 1900 home!

      Thanks so much for your encouraging comment on the blog. The world needs more of that!

      I hope you’re having a wonderful week and I hope your DIY projects are going amazingly!
      -Alyssa at The Craftsman Blog

  10. This is absolutely genius! I’ve lived in my house since 2002 and have always struggled to find the studs. I used a small magnet that’s used for a bike computer hung from some dental floss, and it adhered to the wall perfectly on the studs!

  11. The most powerful magnet I own turns out to be the magnetic “key” to a child-safety cabinet lock — it can lift about 6 or 7 pounds. I’ve been able to find studs by sweeping it around directly by hand.

    The current challenge is a wall where this isn’t working. Knocking isn’t working (wall sounds progressively more hollow as I sweep left.) No electrical boxes. So: Dangle the very powerful magnet on a string.

    …I can’t get it to face the wall. It’s acting as a compass, dangling from that string, and the wall is not North! D-:

    (I did eventually get it to work! The trick is to tape a stiff piece of paper to it to act as a surface guide and prevent it from rotating.)

    1. Oh jeez. Amazon sells rare earth magnets for $10 – they’re incredibly powerful, they can hold 120lbs and will easily find the nails in your studs behind the wall.

    2. I’ve tried the Hanson to absolutely no avail… same dangling problem.

      Could you clarify WHERE you take a stiff piece of paper? On the magnet/finder itself?


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