If you need to screw something to the wall that requires the screw to bear considerable weight, you will need to screw into one of the wooden studs behind the drywall. Typically you would use an electronic stud finder to detect the edges of the studs, but if you don't have one and aren't inclined to go out and buy something you're rarely going to use, you can use this trick to quickly and reliably find studs.
You will need:
- A small strong magnet
- About a 1-2 feet of string or dental floss
- Some tape
I'm not going to bother making a bunch of steps for this; it's extremely simple.
How to make it
Tape the magnet to the end of the string.
How to use it
- Hold the stud finder like a pendulum, and swing it back and forth along the wall. You'll want it to swing so it covers an arc that is at least a foot or so wide.
- Move your hand slowly up the wall so the magnet scans a path along the wall. The magnet will stick to any nailheads in the wall. These nailheads are the ones used to hold the drywall or sheetrock to the studs.
- Once you find a nail, mark it with a pencil or with another small magnet. It helps to re-center your sweep path over the magnet for the highest probability of finding others.
- When you find a vertical column of 2-3 or more nailheads, you can know for sure that you've found a stud. If you find isolated nails that aren't in a column of evenly spaced nails, you probably found a random mis-placed nail that got painted over.
Note: according to building codes and conventions, studs are spaced 16" apart in the United States. If you find one column of nails along a stud, and you need another one, start your next search path some whole number multiple of 16" over.
Superiority of this approach
Besides being very inexpensive and ready to use with very little preparation, this approach has some compelling benefits compared to using a conventional stud finder.
- It detects studs with very high reliability. Evenly spaced nails in a column along your wall almost certainly indicate the presence of a stud behind the drywall.
- Using this method, you also know where the existing nails are, so you can avoid driving a nail or screw into one of them.
- Unlike a sensitive stud finder, you can't tell where the edges of the stud are, so you'll have to guess where the center of the stud is based on the best-fit vertical line using your data points/nail heads.