You don’t have to go fishing for tips—our guide will show you all you need to know
When houses are newly built, electricians install the wiring before the drywall goes up and the insulation is installed. But as time goes on, you may discover a need to install a new outlet or switch—maybe you bought a new appliance, you’re reconfiguring a room, or your family’s need for power sources has simply grown. In that case, you’ll need to fish wire through an existing wall. But what if there’s insulation blocking the way?
Knowing how to fish wire through an insulated wall can save you from having to call an electrician every time you need to install a new outlet. The insulation—particularly fiberglass insulation and foam insulation—can make the job a little more difficult than if you were snaking wire through an interior uninsulated wall, but it’s totally doable even for novice to moderately experienced DIY homeowners.
Below, we’ve put together eight tips covering how to fish wire through an insulated wall. Happy fishing!
Correctly installing insulation can be difficult. Health and safety risks are involved; therefore, we highly recommend contacting a pro to ensure the job is completed safely and correctly.
Before taking on any electrical work yourself—whether you’re installing recessed lighting or moving an outlet—you should check with your local building inspector. They’ll ensure everything you’re doing is up to code.
This tip may seem obvious, but it’s still important to state: Always turn off the power before working with wiring. You don’t have to turn off the electricity to the whole house. Just use the circuit panel to isolate the outage to the room where you’re working.
To be safe, we recommend using a voltage tester to ensure power truly is off before beginning work. This is one of many tools for electrical work all homeowners should have.
Your walls may have fiberglass insulation, but they could also have blown-in cellulose insulation or some kind of spray foam insulation. It’s important to know what type of insulation you’re dealing with—in certain cases, the insulation may be too difficult for a homeowner to handle on their own.
Fiberglass batts should theoretically be installed with the paper backing toward you, with the “fluffy” pink bit facing outward. If that’s how yours is installed, you won’t have to worry about your wire snagging on the insulation, and it should be an easy project. However, fiberglass batts aren’t always installed right (that is, you may find the “fluffy” bit is facing toward you), so you may have to contend with some tougher-to-navigate insulation when feeding the wire through the wall.
Cellulose insulation is easy enough to fish wire through because it’s loosely packed, though glued-in cellulose may provide more problems. (If you’re ever weighing the pros and cons of cellulose insulation, particularly blown-in, remember how beneficial the loose packing is for running wires down the road!)
Foam insulation can pose more problems. Specifically, closed cell—a dense type of spray foam—is nearly impossible to work with as a DIYer. If you have foam insulation, you may need to call in the pros.
Fishing wire through a wall requires something called fish tape. Fish tape is great for interior walls that don’t have insulation, but you may run into trouble if you’re snaking cables through foam and fiberglass insulation because the fish tape can snag.
In that case, you’ll want to use a fiberglass rod that has a bull-nose tip. These flexible rods can guide your wire through the wall cavity and can more easily move through the insulation. Make sure the rod is long enough for the section of vertical or horizontal wall you’re passing through.
Fishing wires vertically is usually easier than horizontally, as you typically don’t have to worry about studs and other obstructions. We’ll cover some more wire fishing tips for horizontal installs below.
A fiberglass rod isn’t the only viable tool when fishing wires through insulation. If you’re having trouble guiding the wire, you may want to try one of two magnetic tools.
With magnetic ball chains or magnetic fishing bits, you’ll be able to guide the wire through the insulation behind the wall.
In the case of the former, you’ll attach a ball chain to the end of the fiberglass rod and feed the rod through the hole. You’ll then use a magnetic retriever tool from the other opening to grab the chain, magnetically, and fish the wire through.
The magnetic fishing bit is also a great tool to try if you’re having trouble. In this instance, you’ll attach the wire to a strong, magnetic leader and fish that through your opening. You’ll then press a second magnet (called a paddle magnet) against the wall to attract the magnet behind the wall. Once they’re “connected,” you can use small, deliberate motions to pull the magnetic leader down toward the other opening.
Fishing wires horizontally through insulation is more challenging because you also have to get through the studs spaced out along the wall. As an alternative, you can remove the baseboard from the bottom of your wall.
Once you’ve removed the baseboard, cut out the drywall that was covered by the baseboard. This will allow you to access the studs. Drill holes through the studs and fish your wire along the wall horizontally.
Just remember to wear proper safety gear (goggles, gloves, and a mask) if dealing with fiberglass insulation. Fiberglass is dangerous: It can cause skin and eye irritation if you come into contact with it, and if you inhale it, it can lead to breathing problems.
Because you’re reinstalling the baseboard, you don’t need to worry about putting the removed drywall back up. No one will see it!
If you don’t want to remove your baseboards, you could move from the floor to the ceiling. Instead of making cuts in your wall, run the wire horizontally outside the wall where it meets the ceiling, then cover it with decorative crown molding.
This way, you don’t have to make cuts, you don’t have to deal with insulation, and your wiring project also adds character to your room with the newly installed crown molding!
Fishing wire through a wall can be tough as it is, but it’s extra daunting when you have to deal with insulation. If you’re not confident snaking the wire yourself, find a trusted electrician near you to do the job.
The fee should be minimal. On average, electricians cost $50 to $100 an hour.
