If 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!
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Step 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.
Step 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.
Step 3: Use a Magnet
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.
You could also try a cool 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.
Step 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.