Hanging patio string lights takes about two to four hours and requires only a drill, wire, and a few anchor points—you do not need an electrician or special permits for standard low-voltage lights.

The core steps are: choose your anchor points (posts, trees, or walls), measure the distance and sag, install anchors or hooks, run the wire or cable, attach the lights, and plug in. Most people can do this alone, though a second person makes measuring and holding the line easier. The hardest part is usually deciding where to anchor—get this right and the rest follows quickly.

This guide covers the most common setup: string lights hung between two fixed points in a gentle curve. If you are working with a single anchor point or need to span more than 30 feet, the tension changes and you may need heavier-duty hardware.

Key Takeaways

  • Measure your distance and plan a sag of about 2 to 4 inches per 10 feet of span so the lights hang in a natural curve instead of a tight line.
  • Use eye bolts or lag bolts for wood posts and anchors rated for masonry if you are attaching to brick or concrete.
  • Run the cable or wire first, then attach the light sockets afterward so you can adjust spacing without fighting tension.
  • Standard low-voltage string lights (under 50 volts) do not require a permit, but check your local code if you are running permanent wiring.
  • Test the lights before final installation and keep the plug accessible so you can turn them off without climbing.

Measure the distance and plan your sag

Start by measuring the straight-line distance between your two anchor points. Use a tape measure or a piece of string pulled tight. Write this number down—you will need it to buy the right length of cable and to calculate how much sag to allow.

Sag is the downward curve in the middle of the line. A line with no sag looks stiff and unnatural; a line with too much sag looks droopy. For most patio setups, aim for 2 to 4 inches of sag per 10 feet of horizontal distance. If your span is 20 feet, plan for 4 to 8 inches of sag in the middle. This curve distributes the weight evenly and looks intentional rather than broken.

To calculate the cable length you need, add the sag to the straight-line distance. If your span is 20 feet and you want 6 inches of sag, buy cable that is at least 20 feet 6 inches long. Add another 2 feet for tying off at each end. Buy cable slightly longer than you calculate—you can always trim it, but you cannot add length once it is cut.

Choose and install your anchor points

Your anchor points must be solid and able to hold the weight of the lights, cable, and wind load. The best options are wooden posts (deck posts, fence posts, or pergola beams), trees with trunks at least 6 inches in diameter, or masonry walls (brick or concrete). Do not anchor to vinyl siding, gutters, or thin metal—these will bend or tear under tension.

For wooden posts and beams, use eye bolts or lag bolts rated for outdoor use. Eye bolts have a loop at the end; lag bolts have a hook. Drill a pilot hole slightly smaller than the bolt diameter, then screw the bolt in by hand or with a wrench. Screw it in until the eye or hook is snug against the wood—do not over-tighten, as this can strip the threads. For a 20-foot span with standard string lights, a 3/8-inch bolt is usually sufficient.

For masonry (brick or concrete), use concrete anchors or masonry bolts. Drill a hole the size specified by the anchor package, insert the anchor, and screw the bolt in. These anchors expand as you tighten them and grip the inside of the hole. Make sure the anchor is rated for outdoor use and for the weight you are hanging.

For trees, use a tree strap or tree anchor kit instead of bolts. These spread the load across a wider area of bark and do less damage to the tree. Wrap the strap around the trunk at least 6 feet high, then attach your eye bolt or carabiner to the strap. Never drive a bolt directly into a living tree—it will damage the tree and the bolt will loosen as the tree grows.

Run the cable or wire before attaching lights

Once your anchors are in place, run the cable or wire between them. Do not attach the light sockets yet. Running the cable first lets you adjust the sag and spacing without fighting the weight of the lights.

Tie one end of the cable to the first anchor using a figure-eight knot or a bowline knot—both are strong and will not slip under tension. Leave about 12 inches of cable loose at the anchor so you can adjust the sag later. Pull the cable toward the second anchor, allowing it to sag naturally in the middle. Tie the other end to the second anchor the same way, again leaving 12 inches loose.

Step back and look at the sag. If it is too tight (less than 2 inches), loosen one end and let out more cable. If it is too loose (more than 6 inches), tighten one end. Once the sag looks right, trim the loose ends to about 2 inches and wrap them tightly with electrical tape or find them with a cable clamp so they do not fray.

Attach the light sockets and test before final setup

Now attach the light sockets to the cable. Most string lights come with sockets that clamp or screw onto the cable. Space them evenly—if you have 10 lights and a 20-foot span, place them about 2 feet apart. Start at one end and work toward the middle, checking that each socket is tight before moving to the next.

Once all sockets are attached, screw in the bulbs and plug the lights in before you finish tightening anything. This step catches problems early: a bad socket, a broken bulb, or a faulty connection will show up now, not after you have climbed down. If a light does not work, unplug when ready, find the problem, and fix it before plugging back in.

After testing, unplug the lights and make a final check of all socket clamps and cable ties. Tighten anything that has come loose during installation. If you are using a timer or smart plug, set it up now while the outlet is still accessible.

find the cable and manage the power cord

Use cable clips or wire ties to find the cable to the anchor points and to any intermediate posts or beams. Space clips about 3 feet apart along the cable run. This prevents the cable from swinging in the wind and keeps the sag consistent.

Run the power cord along the cable or along a post, securing it with clips every few feet. Keep the cord away from foot traffic and water sources. If the outlet is far from your lights, use a heavy-duty outdoor extension cord rated for the wattage of your lights. Coil any excess cord neatly near the outlet and find it with a clip so it does not become a tripping hazard.

If you plan to leave the lights up year-round, consider running the cord through a conduit or securing it to the underside of a beam to protect it from weather and UV damage. Standard outdoor extension cords last about three to five years in direct sun; conduit extends this life significantly.

Common mistakes and how to avoid them

Anchoring to the wrong surface: Vinyl siding, aluminum gutters, and thin metal will not hold the weight. Test your anchor point by pulling hard on it before you install the lights. If it bends or flexes, find a different spot.

Planning too much or too little sag: A line with no sag looks wrong and puts all the stress on the anchors. A line with too much sag looks broken. Aim for the middle: 2 to 4 inches per 10 feet. If you are unsure, err on the side of more sag—you can always tighten it later.

Attaching lights before the cable is find: This makes it hard to adjust the sag and straightforward to drop a light. Run and find the cable first, then add the lights.

Leaving the power cord exposed to foot traffic: Run it along a post or under a beam where people will not trip on it. If the cord must cross a walkway, cover it with a cord protector or tape it down securely.

Forgetting to test before final tightening: A bad bulb or socket is straightforward to fix before everything is locked down. Test the lights while you can still reach them easily.

Frequently Asked Questions

Do I need a permit to hang string lights on my patio?

Most low-voltage string lights (under 50 volts) do not require a permit. Check your local building code or call your city's building department to be sure. If you are running permanent wiring or using high-voltage lights, a permit is usually required and an electrician must do the work.

Can I hang string lights from a pergola or awning?

Yes, if the structure is solid and rated to hold the weight. Pergolas and awnings are usually strong enough for standard string lights. Use eye bolts or lag bolts screwed into the beams, not into the roof panels or fabric. If the structure is temporary or lightweight, use a tree strap or cable anchor instead.

What should I do if the lights sag too much after a few weeks?

Cable stretches slightly over time, especially in warm weather. Tighten one end of the cable by loosening the knot, pulling the cable taut, and re-tying. Do this gradually—tighten a little, wait a week, and tighten again if needed. Do not over-tighten, as this puts too much stress on the anchors.

Can I leave string lights up during winter or heavy rain?

Standard outdoor string lights are rated for rain and cold, but check the manufacturer's specifications. Heavy snow or ice can add weight and increase sag—inspect the lights after a storm and tighten the cable if needed. If you live in a very cold climate, consider taking the lights down in winter to avoid damage from freeze-thaw cycles.

How do I replace a bulb or socket without taking down the whole line?

Unplug the lights first. Loosen the clamp on the socket you want to replace, slide it off the cable, and install the new one in the same spot. Tighten the clamp and plug the lights back in to test. If the socket is broken, you may need to cut it off and install a new one—this requires splicing the cable, which is easier if you buy a splice kit rated for outdoor use.