Key Tips for Wiring an Unfinished Garage

How does your unfinished garage look? Is it well-lit? Does it have enough outlets for your tools and gadgets? Or are you relying on extension cords to reach the far corners? I once had an unfinished, detached garage built back when Model T cars were the latest innovation. Even though I’m a licensed electrician, I never bothered updating it. But looking back, I could have— and you can too. In fact, wiring an unfinished garage could be one of the best upgrades for your home.

Garage wiring requirements are updated periodically, and each jurisdiction follows different code cycles. It’s a good idea to check with your local permitting office to understand what code cycle they enforce. The following guidelines are based on the 2023 National Electrical Code (NEC), but they’re not exhaustive. If you’re uncertain or uncomfortable working with electricity, don’t hesitate to call in a professional.

Do I Need a Permit to Wire My Garage?

You might need a permit— it depends on your city’s rules. In my area, I can install up to six receptacles and/or one new circuit on my own home without needing a permit. However, each city has different regulations, and many places require licensed electrical contractors to obtain the permit, even if the homeowner can do the work themselves. And if you need a permit, remember you’ll also need an inspection once the work is done.

Garage Wiring Basics

Garage wiring requirements change frequently because our needs are evolving— tools are getting bigger, and electric vehicle (EV) chargers and other garage accessories are becoming more powerful. Below are the 2023 NEC basics, along with some general wiring tips.

Branch Circuit Requirements

Both attached and detached garages need at least one 20-amp circuit to power receptacles. If you have a single-car garage, you can also power the lights with this circuit. However, for garages with multiple “vehicle bays,” this 20-amp circuit is dedicated solely to receptacles— you cannot use it to power lights or other devices. It’s fine to add additional circuits, as long as they are 15 amps or greater.

Many houses built in the last 10 years might only have a 15-amp circuit in the garage, since the 20-amp requirement was added in 2017. But if you use power tools or have an EV charger, you probably understand why the NEC increased the circuit amperage: these devices draw a lot of power. If everything is on a 15-amp circuit and you start running a high-demand tool or charger, the breaker will likely trip.

Speaking of EV chargers, any charger over 16 amps must have its own dedicated branch circuit, which means it should not share a circuit with anything else.

Receptacle Requirements

The NEC requires at least one receptacle for each vehicle bay, and they must be no higher than 5 1/2 feet from the floor. These receptacles should be powered by the 20-amp circuit, but you can add more receptacles to this circuit or install separate circuits for additional outlets. You can even add outdoor receptacles to your garage circuits.

Each receptacle— inside the garage and outside— must be protected by a ground fault circuit interrupter (GFCI), either in the form of a breaker or a receptacle. It’s important to install GFCIs in easily accessible locations; don’t place a GFCI receptacle in an awkward spot, like behind the fridge or on the ceiling near the garage door opener. For those hard-to-reach spots, use a GFCI breaker.

Lighting Requirements

Your garage must have a lighting outlet controlled by a listed wall switch or controller. This light should not be powered by the 20-amp circuit used for receptacles unless you have a single-car garage. You’ll also need a lighting outlet outside any exterior door that’s accessible from ground level. Using a three-way switch for the interior light can be convenient, as it allows you to turn the light on or off from either entry door, though this is not mandatory. The exterior light can be controlled by a switch, remote, central, or automatic means.

One thing to consider: If you wire the lights and receptacles on the same circuit and the GFCI trips, you’ll be left without both power and lighting until the breaker or receptacle is reset. For this reason, many electricians recommend running lights on a separate branch circuit.

Protect Your Wiring

The NEC requires that exposed non-metallic sheathed cable (NM-B), also known as Romex, be protected from physical damage. Unfinished garages are full of things that could damage your wiring, leading to potential safety hazards. People often ask if they can run cables vertically alongside or horizontally through studs in a garage. The answer is yes, but you need to follow certain guidelines.

• Maintain 1-1/4 inch depth: Keep the cable at least 1-1/4 inches from the edge of wooden studs, joists, or rafters, and never staple it to the face of framing members where it could get snagged by something.
• Use nail plates: If you can’t maintain the proper depth when drilling holes in studs, use protective nail plates to prevent nails or screws from damaging the cable. If you have metal studs with pre-punched holes, add bushings where the NM-B cable passes through.
• Be cautious with finished walls: If your garage has concrete block or finished drywall walls, consider using conduit or metallic sheathed cable instead of NM-B. The NEC requires protection against physical damage “where necessary,” and this can sometimes be a judgment call.
• Support your cables: NM-B should be secured every 4-1/2 feet. You can’t let cables hang unsupported in the ceiling, and when running cables through studs horizontally, this provides support.
• Secure cables near boxes: Secure the NM-B cable within 12 inches of boxes unless you’re using a single gang, non-metallic box without integrated clamps. In that case, secure the cable within 8 inches of the box.

Key Tips for Wiring an Unfinished Garage

If you’re tackling wiring your unfinished garage, there are a few things to keep in mind to ensure safety and functionality. Key Tips for Wiring an Unfinished Garage include keeping your cables protected, meeting all NEC requirements, and ensuring you add enough power for modern needs like EV charging and heavy-duty tools.

You don’t have to settle for a dimly lit, poorly equipped garage. By following these tips and understanding the basic wiring requirements, you can transform your garage into a fully functional space. If you need to upgrade or overhaul your garage’s electrical setup, Key Tips for Wiring an Unfinished Garage can help guide you through the process, ensuring everything is up to code and safe.

Lastly, if you’re ever in doubt about how to proceed, consulting a professional electrician can help ensure your work is safe and meets all local codes. Happy wiring!