From time to time, certain projects require drilling holes into the walls of a home. For example, drywall anchors, commonly used for hanging pictures and other décor, typically require a hole to be predrilled before anchor installation. Drilling holes may also be required to hang heavier items such as TV mounts, surround sound speakers, and mirrors, to name a few, so they can be securely anchored into the framing behind the drywall. Care must be taken when drilling into the walls of a home, as hazards may lie just below the surface. Common in-wall hazards include electrical wiring, hot and cold water lines, drain pipes, and natural gas lines—the following aims to shed light on these potential hazards and how to avoid drilling into them.
Typical Wiring Patterns in New Homes
Electrical wiring exists as the most widespread hazard when it comes to drilling through walls. Every outlet, light switch, wall sconce, etc., has at least one run of wire going to and from it. As a general rule of thumb, wiring for light switches runs vertically up the wall to the ceiling above, where it is routed to the appropriate light fixture. Wiring for outlets around the lower wall section can run either vertically down from the ceiling or horizontally through the studs from one outlet to the next. In multi-level homes, these wiring runs may come from the floor below instead of coming down from the ceiling.
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.1 Limiting drilling depth to less than 1-1/4 inches is a good start to reducing the risk of damaging wiring behind the drywall.
The 2018 International Residential Code also requires steel plates or sleeves to be installed to protect wiring that is run horizontally through the studs in the wall.1 These plates are applied where the wire passes through to prevent drill bits or fasteners from contacting the wire at stud locations. Therefore, if significant resistance is encountered when drilling through the drywall at a stud location, it may be due to one of these protective plates, and drilling should be stopped.
How Are Pipes Run Through Walls?
Like the electrical wiring running throughout a home, plumbing tubing and pipes are hidden just behind the drywall. Every plumbing fixture in a home, whether a shower, sink, washing machine, or others, has water supply lines and waste drain piping running to and from them. In addition to water lines, HVAC refrigerant lines and natural gas plumbing are also located in many homes’ walls. Therefore, the same care taken to avoid electrical wiring must also be considered to avoid plumbing lines.
In general, plumbing lines run either down from above or up from below to supply fixtures and appliances. There are exceptions, such as multiple fixtures in close proximity on the same wall and restrictive floor plan layout. In some scenarios, the plumbing lines may be run horizontally through the wall framing. Much like the safeties in place for electrical wiring, the 2018 International Residential Code also requires plumbing lines to be protected by steel plates in locations where they pass through framing members and are closer than 1-1/4 inches to the edge of the framing member.2
It is important to remember that plumbing fixtures may not be visible from both sides of a wall. Prior to any drilling, ensure the wall cavity is free from any plumbing fixtures by inspecting both sides of the wall at the proposed drilling location. This inspection also extends to exterior walls, as a hose spigot may be located on the exterior of the home.
Having a couple of standard tools on hand can significantly reduce the chances of drilling into wiring or plumbing. The first and simplest tools are a tape measure and a piece of masking tape. Generally speaking, the sheetrock used for wall application is ½ inch thick. Therefore, an easy way to limit drilling depth is to measure just over half an inch back from the drill bit’s tip and apply a masking tape “flag.” With a tape flag applied, a consistent, safe drilling depth is achieved efficiently. If you’re installing drywall anchors using a longer screw, it is best to drive it by hand using a screwdriver.
Another great tool to keep on hand is a stud finder. Many of the stud finders on the market today are sensitive enough to register not only the framing lumber behind the drywall but also the signature of electrical wiring and even some plumbing. Of course, a stud finder is not a foolproof way of identifying every electrical or plumbing hazard in the wall. Still, it may pick up a signal strong enough to warrant further investigation.
The type of drill bit being used must also be taken into consideration. Standard twist drills with a 118-degree or 135-degree cutting angle are preferred in most applications. Spade bits and Forstner bits cut more aggressively and can more easily damage wiring and plumbing below the surface of the drywall. Using the tape flag described above on a standard twist drill is a safer choice.
- Before drilling any holes, ensure access is available to the water and gas shut-offs for the home.
- If applicable, turn off breakers for the electrical circuits feeding the work area (ensure additional lighting is available if required)
- Do not drill any deeper than is needed (1/2-inch for typical residential drywall)
- Do not drill directly above, below, left, or right of any switches, outlets, or plumbing fixtures
- Inspect both sides of the wall for possible hazards prior to drilling
Installing a big screen TV, a mirror, décor, or family photos on the wall is a great way to make a house become a home. Many of these items require holes to be drilled into the home’s walls.
While there is no “one size fits all” rule for drilling holes in the walls of a home, the guidelines presented above should significantly reduce the chances of encountering the hazards that lurk behind the drywall.