Even beginner metal detectorists know that you can use machines to search for objects buried underground or in the sand at the beach. However, you may need to learn that some metal detectors can sense metal in even denser, harder surroundings such as brick or concrete.
High-quality metal detectors with large search coils can work through brick and concrete, but usually, they can only sense metal objects eight inches (20 cm) deep in these denser materials.
In this article, I’ll explain if metal detectors can work through brick and concrete, under what conditions metal detectors work through these materials, and offer some tips.
Do All Metal Detectors Work Through Brick and Concrete?
Not all metal detectors can work through brick and concrete. High-quality metal detectors with large search coils can usually sense metal through these barriers, but only up to eight inches (20 cm) of depth.
Metal detection technology has come a long way, and sophisticated metal detectors can penetrate dense materials, including concrete and brick. However, not all metal detectors are capable of such a feat.
Cheap metal detectors have their uses and advantages, but they probably won’t be very useful for going through brick or concrete. For more information, check out my article on whether you should buy a cheap metal detector: Are Cheap Metal Detectors Worth It?
More expensive and advanced metal detectors, though, can detect through brick and concrete. However, they are still limited in terms of the depth they can reach. Even the best metal detectors won’t be able to reach as far through brick or concrete as they’d be able to reach through soil. Most detectors likely won’t be able to sense any metal that’s more than eight inches (20.32 centimeters) deep in the dense material.
Finding Rebar in Concrete
Suppose you’re looking for a specific object in concrete. In that case, you might only get signals from the Rebar. Rebar stands for reinforcing bar, and it is commonly found in concrete because it increases the concrete’s strength and allows it to resist wear and tear, including cracking. Rebars help distribute the weight more evenly, which allows concrete structures to stand for longer and support more weight.
Rebars are usually made of steel, so if you’re waving a metal detector over a concrete structure with these rebars, you’ll likely get overwhelmed by the response because the detector will sense the steel.
Finding the Rebar might be your goal in using a metal detector on concrete. Accurately identifying Rebar is an important step in surveys of reinforced concrete structures. If you want to make any changes to a concrete building or install utilities, it is important to know where these reinforcements are. Knowing where the rebars are helps you avoid damaging the reinforcing material and the structure’s overall stability.
Metal detectors are great tools for locating the general location of a rebar. However, if you need absolute precision, I recommend using a different tool, such as a rebar locator or a ground-penetrating radar concrete scanner.
Does Coil Size Matter?
The metal detector needs to be high-quality (and usually expensive) to work through brick and concrete, and it also needs to have a large search coil. Larger search coils can go deeper than smaller coils, so they’ll be able to work through the density of stone or concrete more effectively. Your search coil should be more than fifteen inches (38 cm) in diameter. A larger coil also limits the number of sweeps you’ll need to do to cover an area.
However, larger coils have less sensitivity to smaller targets, so if you’re hoping to find a smaller object within the concrete or brick, you’re probably out of luck. Even with a smaller coil, it would be difficult for a metal detector to penetrate through thick brick and concrete and sense a small item.
Here are the various metal detector coil sizes available on the market:
- Small (less than five inches (13 cm) in diameter). Small coils are good to use in areas littered with lots of trash. They are better at distinguishing between desirable and undesirable objects. It’s also easier to detect in tighter or less reachable areas with a smaller coil.
- Small-medium (five to eight inches (13-20 cm) in diameter). These coils are best for areas with highly mineralized soil. They are a little less good at discrimination than the smallest coils but still better than larger coils.
- Medium (eight to twelve inches (20-30 cm) in diameter). Most metal detectors come with a medium-sized coil. This coil size is good for general use because it covers a lot of ground, can reach reasonable depth, and is somewhat good at discrimination.
- Large (twelve to twenty-four inches (1-2 feet) in diameter). I suggest using coils in this size category for working through brick and concrete. These coils can reach the highest depths, which is essential when working with dense material. However, you don’t necessarily need a twenty-four-inch (2 ft) search coil. Most detectorists find that the depth range doesn’t increase beyond a fifteen-inch (38 cm) search coil.
I also recommend using a metal detector with a circular coil if you plan to try to detect through brick or concrete. Circular coils are more stable and perform better than elliptical or open web coils.
Tips for Metal Detecting Through Dense Materials
Getting a metal detector to work through brick and concrete is a challenge. The most important part has the appropriate tool, but beyond splurging on a high-quality metal detector, there are other things you can do to increase your chances of success. Here are some of my top tips for metal detecting through brick and concrete:
- Move the metal detector slowly. You want to give the detector the best possible chance of detecting something in the brick or concrete, so give it the proper time to survey the area and reach any metal. You should keep your swings slow and consistent throughout your search.
- Turn down the sensitivity. You’ll want to reduce electrical interference as much as possible when using your metal detector on dense materials. The best way to do this is to turn down the sensitivity. I recommend completely calibrating your metal detector before using it on brick or concrete. For calibration tips, check out my article on how often metal detectors should be calibrated: How Often Should Metal Detectors be Calibrated?
- Check the blueprints. If you’re looking for specific pipes or rods, consult the building’s blueprint if you have access to it to get a general idea of where you should locate that particular object. This step will reduce the guesswork and help you get a reasonable starting point.
- Test your metal detector first. Before you rely on your metal detector working through brick and concrete, run a test to see if your metal detector is up to the task. Place a nail behind a concrete wall and run the metal detector over it to see if you pick up a signal. If you don’t get anything from your detector, it may not be of high enough quality to work through dense material.
Following these tips doesn’t necessarily guarantee success when metal detecting through brick and concrete, but these actions help.
Not all metal detectors can work through brick and concrete, but high-quality metal detectors with large search coils typically can. However, they usually don’t work at depths larger than eight inches (20 cm), and if you’re trying to detect through concrete, you’ll likely only get signals from rebars. If the metal detector has a large search coil, it’s more likely to work through dense materials.