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Why Your Stud Finder Is Showing False Positives (And How To Avoid It)
False Positive
A stud finder at times returns an incorrect reading, indicating a 2-by-4 stud is at a certain location, but when you drill there, you find nothing behind the drywall.
This happens when it finds an electrical conduit, wires, pipes, stray screws, or even nearby items instead of a 2-by-4. If you’re unsure, follow these steps before drilling.
Don’t assume the first hit you receive is a 2-by-4 stud. Scan the area multiple times with varying patterns of movement until the stud finder keeps registering the same spot.
Whenever the tool returns a hit, mark the spot with a pencil. You can then find each mark as you work in overlapping sections, so you can feel confident the location is correct.
Most often, 2-by-4s that make up drywall framing are placed exactly 16 inches apart from the center of the edge of one board to the center of the edge of the next board.
Once you’re certain the stud finder has located a stud, measure 16 inches outward on either side of it to help you locate others, then verify their location with the stud finder.
Use clues in a room design to work out the most likely location of wall studs. For example, electrical outlets must attach to a 2-by-4 wall stud to comply with building codes.
Avoid drilling into those 2-by-4s, as you may hit an electrical wire. You can locate them using the stud finder, then use the 16 inches on center method to find nearby studs.
If the room has shelves or a towel bar, they’re probably screwed into a stud, so verify that with the stud finder, then use the 16 inches on center method to find nearby studs.
The main 2-by-4s in your wall frame will run vertically behind the drywall, so if you’re detecting studs running horizontally, you’re probably receiving a false positive.
The 2-by-4s will also be straight. If the stud finder indicates they’re curved or change directions, you're probably receiving a false positive from electrical wires or plumbing.