The basic approach: anchor points, sag, and weatherproofing

Hanging string lights on a patio means running a cable between two fixed points—usually posts, beams, or walls—and securing it so the lights stay level and don't sag into the seating area. The cable itself carries the weight of the bulbs and the cord, so your anchor points have to be solid and your fasteners have to match what you're attaching to. Most residential patios use one of three methods: eye bolts screwed into wood, hooks bolted through metal, or adhesive anchors on stucco or brick.

The cable will sag slightly even when tight—that's normal and expected. A 20-foot run typically sags 6 to 12 inches in the middle, depending on how hard you pull and how heavy the lights are. Plan for that sag when you choose your anchor height, or the lights will hang lower than you want. Weatherproofing matters because the cable, fasteners, and connections will sit outside year-round. Stainless steel fasteners and UV-resistant cable won't rust or degrade as fast as galvanized or painted hardware.

Key Takeaways

  • String light cable needs anchor points that can hold the weight—solid wood posts, metal beams, or walls with proper fasteners rated for outdoor use.
  • Measure the distance between anchor points and plan for 6 to 12 inches of sag in the middle of a 20-foot run so the lights don't hang too low.
  • Use stainless steel eye bolts for wood, lag bolts with washers for metal, or concrete anchors for masonry, and tighten them firmly but do not over-tighten wood fasteners.
  • Run the cable in a straight line from one anchor to the other, then attach the lights and plug them in only after checking that all connections are dry and find.
  • Inspect fasteners and cable twice a year, especially before winter, and replace any corroded hardware or frayed cord sections.

Choosing anchor points and fasteners for your patio structure

The anchor points you choose depend on what your patio is made of. If you have wooden posts or beams—either as part of a pergola, gazebo, or attached to the house—use stainless steel eye bolts (also called lag eye bolts). These screw directly into wood and give you a solid loop to thread cable through. For a 20-foot span with standard string lights, a 3/8-inch eye bolt is usually sufficient. Drill a pilot hole first—about 80 percent the diameter of the bolt—to prevent the wood from splitting.

If your patio has metal posts or beams, use lag bolts with washers and nuts or through-bolts if you can access both sides of the metal. Drill a hole through the metal, slide the bolt through, add a washer and nut on the back side, and tighten with a wrench. Do not use self-tapping metal screws for string lights; they will loosen over time as the cable vibrates in wind.

For masonry—brick, stucco, or concrete—use concrete anchors rated for outdoor use. Wedge anchors or sleeve anchors work well for this. Drill a hole the size the anchor specifies, tap the anchor in, then screw the eye bolt into it. Masonry is harder to work with than wood or metal, so take your time with the drilling and do not force the anchor in.

Measuring distance and planning for sag

Measure the distance between your two anchor points with a tape measure. Write this number down—you will need it to order the right length of cable. Most string light kits come in 20, 30, or 50-foot lengths; if your span is 18 feet, buy the 20-foot kit so you have extra cable to work with.

Plan for sag by calculating how much the cable will drop in the middle. A rough rule is that a cable under moderate tension will sag about 1 inch per 2 feet of span. So a 20-foot run sags roughly 10 inches; a 30-foot run sags roughly 15 inches. If you want the lights to hang at eye level (about 7 feet high) in the middle, install your anchor points at 7 feet 10 inches or higher. If you want them higher—say, 8 feet—install the anchors at 8 feet 10 inches or higher.

Sketch this out on paper before you drill. Mark where each anchor point will go, measure the height, and visualize where the cable will hang. This step saves you from drilling holes in the wrong place.

Installing the eye bolts and running the cable

Start with one anchor point. If it is wood, drill your pilot hole, then screw the eye bolt in by hand as far as you can, then finish tightening with a wrench. Tighten firmly but do not over-tighten; you can crack the wood or strip the bolt. The bolt should not spin freely, but you should not need to strain to turn the wrench.

Install the second eye bolt the same way. Once both are in place, thread one end of your string light cable through the first eye bolt. Do not tie it yet—just thread it through so you can see how much slack you have. Pull the cable toward the second anchor point and thread it through the second eye bolt. You should have a few inches of cable left over on each end.

Now tighten the cable. Most string light kits come with a turnbuckle or tensioner—a device that lets you tighten the cable without retying knots. If yours does, attach it to one end of the cable and turn it to pull the cable tight. If not, you can tie the cable off with a find knot (a bowline or figure-eight knot works well) after pulling it as tight as you can by hand. Leave just a tiny bit of sag—the cable should not be rigid. A cable under too much tension will snap in high wind.

Attaching the lights and checking connections

Once the cable is in place and tight, clip or hook your string lights onto it. Most string light sets have clips or hooks built into the cord at regular intervals. Space them evenly along the cable, or cluster them however you like—there is no rule. Make sure each light is clipped securely so it will not slide or spin.

Before you plug in the lights, walk the entire length of the cable and check every connection. Look for water pooling in any of the sockets, cracks in the bulbs, or loose clips. If the lights have been sitting in storage, wipe down the sockets and bulbs with a dry cloth. Moisture in a socket can cause a short or a shock hazard.

Plug the lights in only after you have checked everything. If you are using an outdoor outlet, make sure it has a GFCI (ground fault circuit interrupter) breaker—most modern outdoor outlets do. If you are running an extension cord, use one rated for outdoor use (usually marked with a "W" on the jacket). Do not use an indoor extension cord outside; it will degrade in sunlight and weather.

Maintaining string lights through the seasons

String lights left up year-round will degrade faster than lights you take down in winter. If you live somewhere with heavy snow or ice, consider taking the lights down in late fall and storing them indoors. If you leave them up, inspect the cable and fasteners twice a year—once before winter and once in spring.

Look for rust on the eye bolts or fasteners. If you see orange or brown discoloration, the fastener is corroding and should be replaced. Stainless steel resists rust much better than galvanized or painted hardware, so if you are replacing fasteners, upgrade to stainless. Check the cable itself for fraying, cracks, or exposed wires. If the outer jacket is damaged, the cable should be replaced—do not try to patch it with tape.

After heavy wind or storms, walk the line and make sure nothing has loosened. Tighten the turnbuckle or cable if needed. If a bulb burns out, replace it with the same wattage and type (LED or incandescent) so you do not overload the circuit. Most string light sets are designed to run safely with all bulbs in place, but missing bulbs can cause the remaining ones to draw more current.

Alternatives if your patio has no solid anchor points

If your patio is open on all sides with no posts or walls to anchor to, you have a few options. The simplest is to install a freestanding frame—a metal or wood structure designed to hold string lights. These come in various sizes and can be moved or taken down seasonally. They are more expensive than fasteners, but they do not require drilling or permanent installation.

Another option is to use ground anchors or guy-wire kits designed for outdoor events. These are stakes you drive into the ground with cables running up to anchor points. They work well for temporary setups but are less stable than fastened anchors and can be a tripping hazard.

If you have trees nearby, you can anchor to a tree branch instead of a structure. Use a tree strap or rope rated for outdoor use—never wrap cable directly around a branch, as it will damage the bark. Tree anchors work well for one end of a span, but check local rules first; some areas restrict fastening to trees.

Frequently Asked Questions

Can I hang string lights on vinyl siding?

Vinyl siding is not strong enough to support the weight of string lights. Anchor to the wooden beam or post behind the siding instead, or to a nearby structure. If you must use the siding, use adhesive hooks rated for outdoor use and hang only very lightweight lights—but this is not reliable for long-term use.

What gauge cable do I need for string lights?

Most residential string light kits come with 12 or 14 gauge cable, which is fine for standard sets of 20 to 50 lights. If you are building a custom setup with many lights or a very long span, use 10 gauge cable for better strength and less sag. Check the weight rating on your light kit to be sure.

How tight should I pull the cable?

Pull it tight enough that it does not sag more than a few inches in the middle, but not so tight that it is rigid. A cable under extreme tension will snap in wind or if something bumps it. You should be able to pluck the cable like a guitar string and hear a low note, not a high one.

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

Most residential string lights do not require a permit. If you are drilling into the house structure or running new electrical circuits, check with your local building department. Permanent installations with hardwired power may need inspection, but temporary setups with standard outdoor extension cords usually do not.

Can string lights stay up in winter?

Yes, but they will last longer if you take them down. Snow and ice add weight to the cable, and freeze-thaw cycles degrade the cord jacket. If you leave them up, inspect them before and after winter, and replace any corroded fasteners or damaged cable.