If you don’t want a quick picture-hanging job to turn into a lengthy plaster repair, it’s important to anchor your fastener to a framing stud.
This is especially true for heavy objects, but even lighter loads can damage delicate plaster. A stud finder can help identify the location of the wood framing hidden underneath vast expanses of walls or ceilings.
What to Look For
Most modern stud finders use electrostatic fields, which measure the absorption of tiny electric charges in a scanned surface, providing a density reading that can distinguish between a cavity and a framing member. When passed across a surface, an LED display and/or sound signals the change in density that indicates a stud.
Most stud finders penetrate up to 3/4″ into the wall, but some allow “deep scanning” of up to 3″ or more. If you have particularly thick wall surfaces (i.e., ones with multiple coats of plaster) or plan to use the tool for ceilings and floors, select a unit that can scan to at least a 1 1/2″ depth. Additional built-in features may include live-wire detectors, bubble levels, laser lights to mark lines, and adhesives to attach the tool to the wall for hands-free usage. Larger models may offer additional features, but keep in mind that they’re heavier and will be more fatiguing to hold over sustained periods of time.
How to Use It
While using a stud finder is pretty straightforward, there are some techniques to ensure greater accuracy. You may need to calibrate it against the surface you’re working on before using it–check the manufacturer’s instructions for how to do this. Many stud finders only detect increases in density, not decreases, so try to calibrate it in a vacant cavity (several inches away from a door or window frame), or test the calibration in a few locations before you start.
Thick plaster and wallpaper coverings, wire lath patches, moisture, foil-backed insulation, and metallic wallpapers can disrupt readings. Go over your work area multiple times to better ensure accuracy. Stud finders are capable of finding other masses, such as plumbing or heating ducts, which you obviously want to stay away from. (Pay attention to the familiar sound and feeling of nailing into a wooden stud so you’ll notice the difference should you accidentally hit another object.)
It’s always a good idea to install your fastener as closely to the center of the stud as possible. Hitting the center of a stud will give you a solid grab, and you’ll avoid potentially hitting electrical wiring that could be secured beneath. Find the center by patiently moving the finder over the area, paying attention to its alerts–you’ll be able to tell where it begins to hit density and then dissipates.
The Bottom Line
Although you don’t need every bell and whistle, buying the best stud finder will give you better luck. Framing and wall surfaces can be tricky in old houses, but a stud finder can offer you some assurance as you hunt for a solid spot.
Contributing Editor Noelle Lord Castle is a preservation consultant, writer, and educator who shares her passion for older buildings at oldhousecpr.com.