Feb 21 , 2019

How to Wire a Finished Garage

Let there be light! And more fixtures, too!

In our garage, we extended conduit from an outlet to add outlets and a hanging fixture over our workbench area. We also removed a ceiling light fixture and extended wiring from it to install eight new fluorescent fixtures. Remember, though, your existing wiring may not be adequate for large power tools like saws or power-hungry appliances like refrigerators or freezers. For these you may have to add a new circuit, a project we won’t cover in this story.

First we’ll show you how to prepare for installing PVC conduit by adding an extender to your electrical box. Then we’ll show you how easy it is to cut and install PVC conduit and push wire through it. Finally we’ll show you how to hook up the outlets and lights and make sure everything is properly grounded.

Installing the PVC is simple, but you’ll need a basic understanding of electrical wiring to safely connect the wires. We’ll show you how we wired our outlets, switch and lights, but if your wiring is different and you’re not sure how to make the connections, consult a wiring manual or get advice from an electrician. Whatever you do, pull a permit so an inspector can check your work.

If you have aluminum wiring, don’t work on it yourself. The connections require special techniques. Call in a licensed electrician who is certified to work with it. For more information, go to cpsc.gov and search for “aluminum wiring”.

Plan the system

The first step is to draw up a simple sketch and figure out how many outlets and lights you plan to add. Keep in mind that there is a limit to how many lights you can add to one circuit. The maximum number of fixtures is determined by the capacity of the circuit, assuming there is nothing else on the circuit that would be turned on at the same time. The maximum wattage of electrical load that can be turned on continuously for three or more hours is 1,440 watts on a 15-amp circuit and 1,920 watts on a 20-amp circuit (which includes a 20 percent reduction for safety).

When your plan is complete, make a list of the materials you’ll need. Below is a list of the parts we used for this project. Use this as a guide for making your own list. If you need a single-gang to 4-in. square steel box extender like the one we used, you may have to special-order it or pick it up at an electrical supplier. Also, match the wire gauge to your circuit. Buy 14-gauge wire if your circuit is protected by a 15-amp circuit breaker and 12-gauge wire if it’s protected by a 20-amp circuit breaker.

It’s easy with PVC conduit

You’ll find a variety of PVC fittings that let you turn corners and run the conduit exactly where you want it.

To add lights and outlets, you could spend days crawling around your attic and snaking wire through walls. But running wire through PVC conduit mounted on walls and ceilings makes the job faster and a whole lot less frustrating.

At home centers, you’ll find a variety of PVC fittings that let you turn corners and run the conduit exactly where you want it; no need to learn the art of bending conduit as there would be with metal. And unlike metal, PVC plastic is quick and easy to cut. If you goof up, you can cut out your mistake and add new parts using couplings. It couldn’t be simpler. And conduit makes your wiring more versatile because you can always add to or reconfigure the wiring later.

Working with PVC

Glue the adapters to the conduit


Cut the conduit and remove any burrs from the inside of the cut end. Swab PVC cement around the inside of the adapter. Press the adapter onto the pipe, twist it about a quarter turn and hold for a few seconds until the glue sets.

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