Essential Tips For Wiring An Unfinished Garage

How are you feeling about your unfinished garage? Is it well-lit? Does it have enough receptacles to plug in your tools and gadgets? Are you relying on extension cords to reach the far corners? I had an unfinished, detached garage that was built when Model T cars were the latest innovation. So, even though I’m a licensed electrician, I never bothered updating it. But I could have, and you can, too— and it might just be a big upgrade to your quality of life.

Garage wiring requirements get updated periodically, and different jurisdictions follow different code cycles. Check with your city permitting office to see what code cycle they enforce. The below requirements are based on the 2023 National Electrical Code (NEC), but they’re not exhaustive. If you have any questions or aren’t comfortable working with electricity, call in a pro.

Do I Need a Permit to Wire My Garage?

You might— verify with your city’s electrical inspector. My jurisdiction allows me to install up to six receptacles and/or one new circuit on my own home without getting a permit, but your city likely has different rules. Many places require licensed electrical contractors to obtain the permit, even if it’s okay for the homeowner to do the work. Remember that if you do need a permit, you’ll also need an inspection when the work is done.

Garage Wiring Basics

Garage wiring requirements change fairly often because our needs are constantly evolving. Tools, electric vehicle (EV) charging and other garage accessories get bigger and more powerful every year. Here are the 2023 NEC basics, and also some general wiring tips.

Branch circuit requirements

All attached garages and detached, powered garages need one 20-amp circuit that feeds receptacles. If you have a single-car garage, you can also power the lights, but for garages with more than one “vehicle bay,” this 20-amp circuit is for receptacles only — you can’t supply the lighting or anything else. It’s perfectly fine to add additional circuits, though, as long as they are 15 amps or greater.

Houses built as recently as 10 years ago might only have a 15-amp garage circuit (the 20-amp requirement was added in 2017). But if you use shop tools or have a portable EV charger, you probably know why the NEC upped the circuit amperage: They draw a lot of power. If everything in your garage is on a 15-amp circuit, and you fire up the table saw or plug in a 16-amp EV charger, the breaker’s going to trip.

Speaking of EVs, any charger over 16 amps must be on an individual branch circuit, meaning the circuit is dedicated to that use only.

Receptacle requirements

The NEC requires one receptacle for each vehicle bay, and they can’t be higher than 5 1/2 feet off the floor. These receptacles must be powered by the 20-amp circuit. You can have more receptacles on this circuit or add additional circuits for other receptacles, but the vehicle bay ones must be on the 20-amp. It’s also acceptable to add outdoor receptacles to your garage circuits (the 20-amp one or any additional circuit you add).

Every receptacle in the garage and outside must be protected by ground fault circuit interrupters (GFCI), which can be breakers or receptacles. Keep in mind that GFCIs must be installed in readily accessible locations, so don’t put a GFCI receptacle on the ceiling by your garage door opener or behind the fridge. Use other receptacles to protect these inaccessible ones, or use a breaker.

Lighting requirements

The inside of your garage (attached or detached and powered) must have a lighting outlet that’s controlled by a listed wall switch or controller. This light cannot be fed by the 20-amp garage receptacle circuit unless you have a single-car garage. You also need a lighting outlet outside any exterior door that’s accessible from grade level. It’s a good idea to use three-way switching to control the interior light so you can turn it on and off from either door, but it’s not required. The exterior light can be controlled by a switch, remote, central or automatic means.

One thing to consider: If you put lights and receptacles together, and something trips the GFCI, you will be left in the dark until you can reset the tripped breaker or receptacle. For this reason, many electricians run lights separately from other branch circuits.

Protect Your Wiring

The NEC requires that exposed non-metallic sheathed cable (NM-B), aka Romex, be protected from physical damage, and unfinished garages are full of things that could snag your wire and cause a fire or shock incident. People often ask if they can run cables vertically alongside and horizontally through the studs in a garage. The answer? Yes, but you have to follow some rules.

• Maintain 1-1/4 inch depth. Keep cable at least 1-1/4 inches from any edge of wood studs, joists or rafters, and never staple it to the face of framing members, where it could get hung up on something you’re carrying.
• Use nail plates. If you can’t maintain a 1-1/4 inch depth when you bore holes through the studs, use nail plates. These protective metal plates attach to the front of the stud to prevent a nail or screw from being driven into the cable. If you have metal studs with pre-punched holes, add bushings when bringing NM-B cable through.
• Use care with finished walls. If you have a garage wall that’s concrete block or already finished with drywall, consider using conduit or metallic sheathed cable instead of NM-B if the run will be within reach of people or tools. The NEC requires you protect NM-B from physical damage “where necessary,” which can sometimes be a judgment call.
• Support your cables. NM-B must be secured every 4-1/2 feet, and can’t be draped over joists or other things in your ceiling without proper support. Running cable horizontally through studs is considered support.
• Secure cables at boxes. Secure NM-B cable within 12 inches of boxes unless you have a single gang, non-metallic box without integrated clamps that’s no more than 2-1/2 inches by 4 inches in size. (In that case, secure the cable within 8 inches of the box).

FAQ

Does the garage door opener need a dedicated circuit?

No. The 2023 NEC allows all receptacles in the garage to be fed from the 20-amp circuit, including one on the ceiling for the garage door opener. You can also add it to any additional circuits. But, if the listing or labeling requires you to use an individual branch circuit, the NEC says you must follow the listing.

Sources

National Electrical Code (2023). National Fire Protection Association.