Don't continue drilling if you believe there is a pipe in that area, as you risk leakage and damage to your home. In homes with attics, you can usually trace where some of the piping starts to know some areas to avoid drilling. Because this is not fool-proof, never drill into a wall where you suspect a pipe to be.
If you are in the stud space on new construction and meet resistance you should stop. If it was wood blocking you would have had resistance the entire depth of your hole. If you met resistance for a bit and then it felt free again, you put a hole in something you weren't supposed to.
Holes should not be drilled directly above, below, or to the side of any electrical switches or outlets. Per the 2018 International Residential Code, electrical wires should be set back no less than 1-1/4 inches from the edge of the framing lumber.
Drilling into walls is generally safe if you've ensured no electrical wires or plumbing are in the area. Use a stud finder with live wire detection, or consult building plans to identify safe spots. Avoid drilling near outlets or switches as wires commonly run vertically or horizontally from these points.
Drilling through a wall is a dangerous aspect of construction, especially if you don't have the correct equipment. It's almost impossible to tell what's behind that seemingly safe structure and hitting a water pipe, electrical wire, or gas pipe can lead to disaster.
Avoid Over-Drilling:
Drill only as deep as necessary for your project. Over-drilling can weaken the wall or damage underlying structures.
Things You Should Know
Nail a sturdy masonry nail into concrete by repeatedly hitting it with a mash hammer—strike carefully and directly to avoid bending the nail. For safety, wear a face mask and safety glasses and gently fasten masonry nails into the wall before you begin hammering with full force.
Once you think you're on point, one last way to confirm that you're into a stud is to predrill a hole through the drywall with a narrow drill bit (think: 1/16-inch sized bit). You'll be able to feel resistance if the bit hits a stud once it passes through the drywall.
A stud finder is a versatile tool that can help you locate both wooden studs and electrical wires in walls. By scanning the wall surface, a stud finder can detect changes in density that may indicate the presence of wires or other obstacles.
Soil Settlement or Subsidence
This phenomenon may be natural or triggered by human activities such as mining or construction work (e.g., foundation digging, drilling). Changes in soil structure caused by these activities can lead to ground subsidence, which may result in cracks in nearby buildings.
“One common rule is to avoid drilling around light switches and sockets, as the electrical wires can go horizontally and vertically around these fixtures,” Williams explains. “You can also get an idea of where wires and pipes run by looking in the attic and basement to see where they go up or down through framing.”
Avoid drilling into concrete that has infrastructure behind it. Drilling where there are water pipes, electrical wiring or ductwork can be dangerous and cause damage.
The only non-destructive way to find out by inspection is to use a stud finder which has an AC wirefinding mode - a decent one will detect the magnetic field from a live AC wire to a depth of an inch or two.
If you want to confirm the presence of a stud, you can drive a small finish nail into the wall at the suspected location. If a stud is present, you should feel resistance as the nail encounters the wood. Depending on the location of the hole, you may need to repair it after you remove the nail.
Most modern outlets are installed with a certain amount of space between the outlet box and the wall surface, so drilling too deep could potentially breach the outlet box itself, causing electrical hazards. Therefore, using a shorter drill bit might be advisable when drilling above an outlet.
Puddles are a clear sign of a burst pipe. Small puddles in one area usually mean a leak, but large pools of water in multiple areas indicates a burst. These puddles often move across rooms or through walls. Burst pipes continuously leak water until the supply is off, so the puddle grows quickly.
Best practices to avoid electrical wires
Use your detection tool to scan the wall or ceiling thoroughly and mark the safe drilling spots with a pencil. Know the warning signs: Electrical wires usually run along the sides of studs and often vertically from outlets or horizontally at the same height as outlets.
Put some tape on a 6mm drill bit at 12mm depth. Only drill that far - it's normally 12.5mm thick (could be 25 if doubled). Have a poke in the hole with a small screwdriver and 'feel' for anything there. Then use Fischer Duopower 6x30mm wall plugs - they will be fine for a mirror.
Don't continue drilling if you believe there is a pipe in that area, as you risk leakage and damage to your home. In homes with attics, you can usually trace where some of the piping starts to know some areas to avoid drilling. Because this is not fool-proof, never drill into a wall where you suspect a pipe to be.
You'll likely know if you drill into a water pipe in your home. If the sound of a screw cutting into something other than wood and plaster doesn't tip you off, the leaking water will. Depending on the hole's size, the water will burble out or stream-line out.
Pipe finders are designed to identify where electrical cables or gas and water pipes are located inside a wall. This is especially helpful if piping isn't visible or when doing building work on a property you're unfamiliar with.