Stud finder

A stud finder (also stud detector or stud sensor) is a handheld device used to locate wood or metal framing studs behind walls. In the United States, walls are typically made of drywall (also called sheetrock), though stud finders can also be used on lath and plaster walls, and in some cases, even tile.

Example of a multi-sensor stud finder, with a Live Wire Meter, by Franklin Sensors.

Stud finders generally fall into two main categories: magnetic and electronic. Magnetic stud finders detect the metal fasteners (such as nails or screws) used to secure wallboard to studs, while electronic models use sensors to detect changes in wall density. Some advanced models incorporate radar or imaging technology for more precise detection.

History

Stud finders have been in use since the early 20th century. The earliest models were magnetic, using internal magnets to detect metal fasteners—such as nails or screws—embedded in wall surfaces and presumed to mark the location of studs.

In 1977, Robert Franklin developed an electronic stud finder that used a capacitor to detect changes in wall density.^[1] His design was manufactured by the Zircon Corporation, which held the patent and remained the sole producer of electronic stud finders until the patent expired in 1998. While innovative, early electronic models were sometimes inconsistent in accurately locating studs.

In 1995, Thomas McEwan patented an ultra-wideband radar system for sensing applications.^[2] This system, based on micropower impulse radartechnology,.^[3][4][5] enabled the development of more advanced scanning tools, including some types of stud finders.

Following the expiration of Franklin’s patent, further advancements were made to electronic stud finders based on capacitive sensing, improving both performance and adoption.

In 2009, David Dorrough introduced a multi-sensor stud finder design, which used an array of sensors to scan multiple points on a wall simultaneously. This approach allowed the device to detect the presence, width, and absence of studs in real time. Unlike earlier models, these devices did not require calibration and were more adaptable to variations in wall construction.

Dorrough later patented ^[6] this technology and founded Franklin Sensors Inc. to commercialize the product.

Magnetic Stud Detectors

Magnetic stud detectors use magnets to locate metal fasteners—such as nails or screws—that are embedded in wall studs. As the magnet moves across the wall surface, it is drawn toward these fasteners; the pull becomes stronger as the magnet approaches the metal. The point of strongest magnetic attraction typically corresponds to the location of a fastener, which may indicate the presence of a stud behind the wall.

To locate a stud, users move the magnet across the wall until they detect a noticeable pull. Magnetic stud finders operate on the assumption that fasteners are driven into the center of studs, although this is not always accurate. Therefore, users often confirm stud spacing by locating multiple fasteners. In many modern buildings, studs are spaced 16 inches apart, measured from center to center.

Magnetic stud finders can be particularly useful in older homes with lath and plaster walls that contain metal mesh, which may interfere with the accuracy of electronic stud finders.

Traditional Electronic Stud Finders

Electronic stud finders use sensors to detect changes in the dielectric constantof a wall. The dielectric constant varies depending on the density and composition of the material behind the wall surface; when the sensor passes over a stud, the reading typically changes, indicating a higher-density area. Some models also include additional features that can detect metal objects or live AC voltage.

Electronic stud finders are commonly classified into two types: edge finders and center finders.

• Edge finders detect the edges of a stud by identifying where the dielectric constant changes. Users must mark both edges manually to determine the center.
• Center finders use more advanced sensors to automatically identify the center of a stud without requiring manual edge marking.

Edge finders

Edge finders are the most basic type of electronic stud finders that use internal capacitive sensors. They function by detecting changes in wall density, allowing the user to locate the edges of a stud or other hidden object behind the wall surface.

Before use, edge finders must be calibrated over an area of the wall that does not contain a stud. Once calibrated, the device is moved laterally across the surface. A change in the dielectric reading indicates the presence of a stud edge. To locate the full width of the stud, the device should be moved from both directions to identify both edges. The center of the stud can then be determined by marking both edges and measuring the midpoint.

Because edge finders typically use a single sensor, they can be prone to inaccuracy. In some cases, the detected edge may be offset by 25 mm (1 inch) or more from the actual edge of the stud.

Center Finders

Center finders use two sensors to measure the dielectric constant of the wall at separate points. When the readings from both sensors match, the device indicates that it is positioned over the center of a stud. This allows users to locate the stud center without needing to mark its edges.

Center finders typically require calibration prior to use. Surface irregularities, such as wall texturing, can affect sensor movement and impair calibration accuracy.

Unlike edge finders, center finders only need to be moved in one direction to locate a stud.

Radar scanners

A 3D imaging stud finder that utilizes RF technology to distinguish between materials behind the wall.

Some modern stud finders utilize radar technology, often based on radio frequency (RF) signals, to distinguish between various materials behind wall surfaces. By analyzing raw signals transmitted and received by their sensors, these devices can classify wall types and detect studs, pipes, wires, leaks, and even motion caused by pests or rodents.[citation needed]

Radar-based stud finders can be useful for older buildings with lathe and plaster walls, where traditional electronic stud finders may be less effective.[8]

One commercially available example is the Walabot DIY 2M, which integrates with a smartphone application to assist users in locating studs, wiring, and other objects concealed behind walls.

Multi-Sensor Stud Finders

Multi-sensor stud finders are a more recent development in stud detection technology and was patented ^[6] by David Dorrough at Franklin Sensors Inc. These devices incorporate multiple sensor plates and employ algorithms to analyze simultaneous readings from different areas of the wall. This design allows for quicker and more accurate detection compared to single-sensor models and reduces the need to move the device extensively across the wall.

Multi-Sensor Stud Finder

Multi-sensor stud finders can detect multiple aspects of wall construction simultaneously, including the center and edges of studs, as well as areas without studs. Some models can indicate varied stud widths and locate multiple studs at once.^[7]

Due to their use of multiple readings, multi-sensor stud finders are less affected by construction anomalies such as uneven paint, textured walls, lathe and plaster, wallpaper, or irregular plaster, which can interfere with the accuracy of traditional edge and center finders. One commercially available example is the ProSensor M210 by Franklin Sensor.

Materials

ProSensor MAX reading through tile.

Most stud finders can detect through thin tile, although the uneven surface of the tile may interfere with the signals. Some versions of stud finders including the Zircon MetalliScanner MT 7 and Franklin Sensor's ProSensor MAX are able to scan through deeper tile.^{[citation needed]} Some stud finders detect through plywood siding or paneling, though thicker walls may require a stud finder with depth capabilities.

Related tools

Multifunction Stud Finder

Combination scanner tools exist which offer both stud finding and electrical wire detecting capabilities. An example of some models with wire-detecting capabilities include Franklin Sensor's ProSensor M210 and Bosch's GMS120 Digital Multi-Scanner.^{[citation needed]}

See also

• Wall stud