Garage, Shop & Outbuilding Wiring
A detached garage usually gets one extension cord too many before somebody calls. The fix is a buried feed and a small subpanel out there, which then lets you add 240-volt circuits for a welder, a compressor or a heater without borrowing from the house. Attached garages are simpler, but they still need their own circuits once a freezer, an opener and a workbench are sharing one.
A detached building, done properly
- A feed sized for what you will run out there eventually, not only what runs today
- Buried in conduit at proper depth, or bored under a drive rather than cutting it
- A subpanel in the building with its own grounding electrode and isolated neutral
- GFCI protection on the receptacles, which garages and shops require
- Dedicated 240-volt circuits for a welder, compressor, lift or unit heater
- Lighting that covers the bench and the bay, not one bulb in the middle of the ceiling
Shop circuits worth planning for
A table saw and a dust collector starting together will trip a single shared circuit every time. We split the bench across more than one circuit, put the dust collector on its own, and leave space in the subpanel for the tool you have not bought yet. Ceiling receptacles for an opener and a retractable cord reel keep the floor clear.
Heat and cold
A garage heater is the usual reason existing wiring will not do. A hard-wired unit heater needs a 240-volt circuit of its own and a disconnect, and the load has to be checked against the whole service before it goes in. A freezer in an unheated garage earns its own circuit too, since it is the last thing you want on a breaker that trips.
Frequently asked questions
Can I run a detached garage on an extension cord?
Not safely, and not for anything permanent. A cord across the yard has no overcurrent protection at the garage end, and it fails the first time a mower or a plow finds it.
What size subpanel does a garage need?
That depends on the tools and whether there is heat. A small shop is commonly served by a 60 or 100 amp subpanel, sized from the equipment list and from what is left in the main service.
Do garage outlets have to be GFCI protected?
Yes, receptacles in a garage require GFCI protection. Current rules also cover a dedicated freezer or refrigerator outlet, which is worth knowing before you plan the layout.
Can you power a garage without digging up the driveway?
Yes. We bore under drives, walks and landscaping and pull the conduit through, so the surface is left intact.
Will a welder or an air compressor run on my existing garage wiring?
Usually not. Both want a dedicated 240-volt circuit sized to the nameplate, while the existing garage circuit is normally a 15 or 20 amp run shared with everything else.
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