How to Buy a Stud Finder

Magnetic vs. electronic stud finders

Magnetic and electronic stud finders work in entirely different ways. A magnetic stud finder locates the metal nails or screws that attach the wall to the stud. By marking several fasteners with the stud finder, the user makes sure the magnet is really finding fasteners, not some other metal inside the wall. This is the simplest type, usually easy to use and effective on simple half-inch drywall.

An electronic stud finder or wall scanner emits an electronic field that detects changes in the wall's density, so it requires calibration to the basic wall thickness. The most useful models warn of electrical wiring inside the wall, an important safety feature if you're not absolutely sure where the wiring lies, as in a remodeling project. A wall scanner may also be able to detect metal -- conduit, copper pipe, etc. -- so you can adjust your hole drilling accordingly. The main drawbacks -- aside from price -- are that electronic stud finders are more complex devices, making for a steeper learning curve. If an electronic wall scanner doesn't work well, it can be tricky and frustrating to figure out whether the problem lies with the tool or the user.

Here's a summary of the pros and cons of these two basic types. Keep in mind that within each type, some models perform better than others.

Even the best stud finders have their limitations. Few will work through tile and none will work through carpeting. Nor can stud finders detect shielded electrical wiring (in conduit, for example) -- though an electronic wall scanner with a metal-detecting mode can locate the outer metal jacketing. Plastic water pipe, unfortunately, is "invisible" to consumer-level stud finders.

Experts recommend scanning the whole wall before drilling any holes. This way you're mapping out the work ahead of time and can notice any anomalies before getting into hot water (not literally, we hope). For safety, turn off any electrical circuits that might have wiring in the wall. With the electricity safely turned off, it's also best to drill a tiny test hole (or probe the wall with a small punch awl) before plunging into the wall with a large bit or jigsaw blade to be sure you'll be drilling a larger hole in the right place.

Factors to consider in choosing the best stud finder

Experts recommend taking these factors into account in selecting a stud finder:

• Magnetic stud finders for simple jobs. A magnetic stud finder is best for the simplest situations, such as half-inch drywall or thin plywood with no wiring or pipes to worry about. If you'll be using it to find studs on different types of walls, or where you are uncertain about what lies behind the plasterboard, a wall-scanning electronic stud finder might be worth its higher cost and steeper learning curve.

• Electronic stud finders require careful use. Even the best stud finder will give inaccurate results if not used according to directions. Where you place your other hand, for example, could make a big difference.

• Lights and beeps are nice features. These signals speed the work and make the tool easier to use in odd positions where the display is hard to view.

• When selecting an electronic stud finder, look for a model that actively warns of live electrical wiring. This is a valuable safety feature. Reviews can point you to models that are most accurate and reliable in that regard.

• A center-finding stud finder is faster than an edge-finder since you don't have to start from one or both edges and calculate the center.

• Automatic calibration is a helpful plus in an electronic stud finder. Some electronic models warn if you try to start scanning the wall over a stud (which would lead to inaccurate results) and recalibrate automatically as needed.