How to Run Underground Wiring to a Garage | Ask This Old House

Electrician Scott Caron shows a homeowner how to bring power to a detached garage.

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Shopping List for How to Run Underground Wiring to a Garage:
- UF (underground feed) electrical cable
- ¾-inch-diameter plastic conduit, used to house cable
- ¾-inch conduit outlet bodies, boxes, and assorted fittings
- Exterior-grade acrylic-latex caulk, used to weather-seal conduit outlet boxes
- Sand and red caution tape, used to warn of the buried cable
- 1 5/8-inch galvanized or stainless-steel screws, for attaching conduit outlet boxes
- Cable staples, used to secure cable to floor joists and wall studs
- GFCI breaker, installed at electrical panel

Tools for How to Run Underground Wiring to a Garage:
- Trenching machine, for excavating trench
- Cordless drill, used to drill holes and drive screws
- 1½-inch-diameter hole saw, for boring hole in house and garage walls
- Plastic pipe cutters, used to cut plastic conduit
- Propane-powered heat gun, used to heat and bend plastic conduit
- Rake and shovel, for backfilling trench
- Hammer
- Wire strippers
- Screwdriver

Steps for How to Run Underground Wiring to a Garage:
1. Call the local utility company and have them check for buried pipes or wires.
2. Rent a gas-powered trenching machine and dig a trench at least 12 inches deep from the house to the garage.
3. Bore a 1½-inch-diameter hole through the house wall and into the basement with a drill and hole saw. Position the hole directly above the end of the trench.
4. Cut a length of ¾-inch-diameter plastic conduit to extend from the bottom of the trench up to the hole in the house wall.
5. If necessary, use a propane-powered heat gun to bend the conduit to conform to the foundation.
6. Attach a plastic conduit outlet body to the end of the conduit.
7. Push a length of UF (underground feed) electrical cable into the conduit, then feed the end of the cable through the hole in the house wall.
8. From inside the basement, pull the cable all the way to the main electrical panel. Secure the cable to the overhead joists with cable staples.
9. Go outside and lay the cable into the trench, running it all the way to the garage.
10. At the garage, repeat Steps 3 through 7 to install the plastic conduit and cable.
11. After feeding the cable into the garage, screw the conduit outlet body to the exterior wall of the garage. Screw the other conduit body to the house wall.
12. Apply exterior-grade acrylic-latex caulk around the conduit outlet body to seal out water.
13. Cover the cable with about 2 inches of sand, then lay caution tape on top of the sand along the entire trench.
14. Backfill the trench with the excavated soil.
15. Have a licensed electrician make the final wire connections in the garage and at the main electrical panel.

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How to Run Underground Wiring to a Garage | Ask This Old House

[tboneproductions]

My dad had a trencher. It was me and my three brothers. R.I.P. dad and thanks for the work ethic😀

[SkilledEddie]

All that work for a single circuit but i'm sure the customer like in most cases wanted to take the cheap way out and do the bare minimum. I always recommend running at least a 30 amp feeder to a garage. People always overload a single circuit in a garage. They start putting extra freezers and fridges in the garage and in the winter run an electric space heater. Then you have all the power tools people use. If you are going to dig up the ground like that might as well spend a little more now then a lot more later. Yeah its' about $150 more for 10-3 vs 12-3 for about $50-$60 for 100 feet but the same labor.

[laura.marcosmatos]

This video answered the burning question I had of how to secure LB box to the wall. Thank you for posting this video. Now I can finish installing my floodlights above my garage!

[GotchaplumberGotchahvac]

Great tip with heating & bending conduit.

Enjoy the show & videos.

[glasshalfempty]

It is...until you need to replace it or run another line. Have fun digging again. Conduit people, CONDUIT!

[philipschmidt]

My brother and I ran wire to a pump house and we didn't take shortcuts or spare expenses! We ran it into conduit pipe! Sand doesn't mean anything to me when I am digging! Plus it saves time having to replace the wire when you cut through it with a shovel or ditch digger!

[heru-deshet]

When I built my house I rand conduits everywhere I might decide to take electric in and outside. Smartest thing I ever did.

[joe]

Code or no code, running wiring under ground should ALWAYS be in conduit.

It's very possible, I'd say highly likely, to keep going past the sand and caution tape without seeing them because they're soft, easily cut with a shovel, and provide zero that shovel can still go right through the electrical line with no problems if someone is digging through without looking. Conduit will provide certain, immediate feedback that something is down there even if you don't see it.

[royhoco]

when I ran electric wire and a water line 200 ft to my garage/workshop it was buried 30" deep. I used 2 0 wire so I could have a 100 amp breaker in the garage and the wire was run in conduit big enough for future wiring if needed, also ran a small rope in the conduit to pull future wires if needed. ran the water piping in conduit due to the rocky soil. it was a beast of a job.

[blueribb]

An electrical conduit would allow for future wire upgrades and such along with protection. CATV, phone and ethernet could be added as needed at a later time. A pull string or cord could be added to assist in adding these cables later.

[danbasta]

I would continue to use PVC pipe going out to the garage with the wire threaded into the pipe to protect it even that much more. I've done it before, threaded the wire into the pipe, and ran the wire out to the junction box into the garage, first, then ran the wire into the breaker box and connect up the breaker in the breaker box. I'm also kinda funny about marking my lines with a black magic marker so they are marked from beginning to end so you KNOW which line is which, and eliminates confusion as well as marking the breaker inside tag so you KNOW how to kill the power if you need to to do further electrical work inside the garage, or to change things that might needing changed or rearranged for the future.

[johndoee]

This show is great. Never knew I could form fit conduit pipe!

[mcarroll]

If you’re going thru all the work of trenching, put the whole run in conduit. Direct burial wire is a bad idea. And your garage door on a GFCI breaker will have nuisance trips.

[j.wat.]

I would've used a heavier wire for drop with a feeder panel in the garage. Then you can add on compressor, and heaters.

[LokarofWS]

I hired an electrician to run an outlet 35 feet from outside breaker box to a hottub. Used a GFCI breaker and that PVC wire laid in the trench. Not only did he do a terrible job, (I had to show him how to tin wire to put an outlet together, provided my tools so he could get the job done, and dug 3/4 of the trench because he was going so slow), but 2 months later, I'm ripping the wire back out of the ground because it seems moles have opened that waterproof protective covering. Glad I didn't dump a load of concrete on top of it! Yes, I told him there were moles in the area and he said "They may think the wire is a root". but did nothing about it.
Once again shows me most contractors are worthless since I have to go back and fix what they screw up 99% of the time. I'm always relearning that lesson. Do it myself so it's done right.

[bitemyram]

“Alright Craig, you ready for it” 😱
😂😂😂

[ThisOldJalopy]

This is what I'm doing this weekend!

[SillyPutty]

I have been doing electrical work for 31 years and had my masters ticket for 24 there is no way i would do this to a client. PVC is cheep digging a ditch is not. Use conduit don't re-dig a ditch.

[peterreynolds]

2017 code says you can't do this no more, for all the homeowners that want to do this now. Garage outlets have to be dedicated 20a gfci. And plus in this installation you need a disconnecting means at the first point of entry.

[BradiKal]

I know a guy who used coaxial cable (yes, cable tv wire) to run power to his garage for a single light bulb . years later we still give him grief for that!