How to Install an Outdoor Lamp Post
Learn how to install an outdoor lamp post; details include digging a post hole, setting the post and wiring the lamp. Whether you want to add a lamp post alongside your front entry or you need to replace an outdated one, this article will provide the necessary steps to complete the job. Not only do lamp posts improve the “curb appeal” of your home, they also add a measure of security.
Check with your local building department before starting the work to see if a permit is required.
Tools and Material:
Hacksaw for cutting CPVC conduit
Posthole digger or auger
Small shovel for the trench
CPVC conduit – 3/4 inch, Schedule 40
Light switch and box, if not already installed
Lamp post and Fixture
1. Locating and Digging the Hole
If you live in colder parts of the country you will need to dig down at least two and half feet to guard against frost heave. This is when the ground freezes beneath the end of a post and push it out of the ground.
The best way to accomplish this is with a posthole digger. If you are planning on installing multiple lamp post, you should rent an auger which is basically a drill designed for digging into the soil. Larger ones are two-man augers, but many home and rental centers rent one-man augers that are attached to a gas-powered engine that rolls on the ground.
If you are confident about your electrical wiring skills, this is a fairly easily installation, otherwise you may want to hire an electrician to run a line to the location you have chosen. You can use direct-burial cable which is rated for underground usage, or run a conduit constructed out of CPVC, basically PVC which is resistant to UV light. You need to bury the conduit at least 12 inches underground in most areas, but in particularly cold areas, 18 inches is recommended. I also like to run a ribbon marker about 6 inches above the conduit or wire to prevent any accidents when digging in the area. You can order it online or visit your local electrical supply house to pick up a roll.
After the hole is dug, pour 2 inches of gravel into the bottom of the hole, to prevent water from pooling under the post.
The post can be aluminum, fiberglass, or wood such as solid cedar. You can also use a pressure treated post, but these are not that attractive and are prone to warping, splitting, and twisting.
You may want to use some concrete to set the post to prevent it from being blown over in high winds or if your ground is very sandy or soft. Use one bag of pre-mixed concrete and follow the manufacturer’s instructions for preparing the mix. You will need to run the conduit up through the center of the hole where you want to the lamp post to be. Use a 90 degree sweep which is a larger fitting that allow you to easily fish the wire through. Typically 3/4 inch conduit is large enough for one wire.
Set up at least 2 braces to support the post, I like to use 2x4 studs with both ends cut on an angle and screw a scrap piece of 2x4 to the end. I use two clamps to hold the scrap pieces of wood to the lamp post and then pound a stake in the ground and screw the other end of the 2x4 to it. This way I can loosen the clamps while I make sure the post is plumb; when it is, I tighten the clamps and pour the concrete. You can also use straps or ropes attached to stakes for a similar effect and they should be at least 2/3 of the way up the post to keep it stable while the concrete sets.
2. Electrical Wiring
Most lamp posts are completely hollow and allow you to run the wire directly through them. You should be able to push the wire through the conduit an up through the post. If you have an extremely long run, you may need to install a pull box in the ground half way to the post or install a wire pulling string in the conduit that you can tie to the end of the wire and pull it from the source to the post.
If you need to run a new wire from your house for the lamp post, make sure that the circuit that you want to tie into is shut off and then double check that it is off. You can come off of the nearest outlet that is not already operated by a switch. You will need to install a light switch box at a height that matches the other switches in your home, around 50 inches above the finished floor. Run a wire from the receptacle to the new switch box and then from the switch to the end of the conduit, most likely in your basement of garage.
You can also have the conduit come out of the side of your house and then install an elbow to have it go directly into the ground at the proper depth. Pulling a wire through 4 bends is the maximum allowed for this application, by coming through the wall and then down into the ground you will have 3 bends, so it should be fairly easy.
3. Light fixture wiring
You may want to utilize the clamps from before to set up a shelf at the top of the post to allow you to rest the light fixture on its side wire you complete the wiring.
Remove the PVC covering from the wire, strip off the wire insulation, secure the wires from the lamp to the wire you ran wire nuts, and then wrap the wires tightly with electrical tape for additional protection from moisture. The tape will also make sure that the wire nuts stay on when you push the wires back down the post.
Place the fixture over the mounting base on the top of the post; usually there are only 2 screws to hold it to the post. Check to make sure that the fixture is level.