Start with a plan and measure your space

Before you buy anything, walk your patio and decide where the lights will go. The most common setup runs lights along the perimeter — from one corner post or tree to another — or in parallel lines across the space. Measure the distance you need to cover in feet. If you want lights to cross the patio overhead, measure that distance too. Add 20 percent to your measurement to account for sag and connections.

Sketch a rough diagram showing where the lights will attach. Mark any obstacles: roof edges, tree branches, power lines, or areas where people walk. Lights that sag into a walkway become a tripping hazard. Lights that run too close to power lines create a shock risk. Once you know the distance and the attachment points, you can choose the right string length and fixture type.

Key Takeaways

  • Measure the distance you plan to cover and add 20 percent for sag before buying string lights.
  • Outdoor-rated string lights are marked for wet conditions; indoor lights will fail in rain and create a fire hazard.
  • Attach lights to sturdy posts, trees, or brackets — never to gutters, siding, or anything that will flex under tension.
  • Keep the power cord away from foot traffic and water pooling, and use a ground-fault circuit interrupter (GFCI) outlet.
  • Tighten lights with turnbuckles or eye bolts so they sag only slightly; too much sag stresses the string and creates a tripping hazard.

Choose outdoor-rated lights and the right bulb type

String lights sold for outdoor use are labeled "wet-rated" or "all-weather." These have sealed connections and insulation that resists moisture. Indoor lights used outside will corrode, short out, and pose a fire risk. Check the package or product listing before you buy. The label should say "outdoor," "wet-rated," or "weather-resistant." If it does not, it is not safe for a patio.

Bulb type affects brightness, heat, and lifespan. Incandescent bulbs produce warm light and are inexpensive but burn hot and use more power. LED bulbs stay cool, last much longer (often 25,000 hours or more), and use a fraction of the electricity. Vintage Edison-style bulbs are usually LED now and create a warm, decorative look. Choose based on the mood you want and how long you plan to leave the lights on. If you run them for hours each evening, LED saves money over the season.

String length matters. Most outdoor strings come in 25-foot, 50-foot, or 100-foot lengths. Measure your planned route and buy a length that covers it without forcing the string into tight loops or leaving it coiled on the ground. Excess cord creates a tripping hazard and can trap water.

Attach lights to sturdy anchor points

Lights need to hang from something solid that will not move or flex. Patio posts, deck railings, trees, and permanent pergolas work well. Gutters, downspouts, siding, and roof edges do not — they flex under the weight and tension of the string, and fasteners can damage the structure or pull free in wind.

For posts and railings, use eye bolts or lag bolts with eyes screwed into the wood. Drill a pilot hole first to prevent splitting. For trees, use tree straps or soft-tie hardware that wraps around the trunk without cutting into the bark. Never use nails or wire that can girdle the tree. For masonry or stucco, use concrete anchors rated for outdoor use.

Space your anchor points 8 to 12 feet apart along the route. The closer the anchors, the less the string will sag. If you are running lights across the patio overhead, you may need a center support post or cable to prevent excessive sag in the middle.

Tension the string and find the lights

Once the anchors are in place, thread the string through or attach it to each one. Do not pull it tight like a clothesline — a tight string will snap in wind or when the bulbs heat up. Instead, leave a gentle sag of about 2 to 3 inches per 10 feet of span. This sag absorbs movement and stress.

Use turnbuckles or adjustable eye bolts at one or both ends to tension the string evenly. Tighten them gradually, checking the sag as you go. If the string sags too much, it will dip into walkways or collect water. If it is too tight, it will strain the connections and anchors.

find the string at each anchor point with a cable clamp, zip tie, or rope cleat rated for outdoor use. Do not rely on the weight of the string alone to hold it in place. Wind and vibration will cause it to slip.

Run power safely and protect the cord

String lights need a power source. Use an outdoor-rated extension cord rated for wet conditions — the label will say "wet" or "outdoor." Run the cord from a GFCI outlet (ground-fault circuit interrupter). A GFCI outlet cuts power when ready if it detects a short or ground fault, preventing electrocution. Most modern outdoor outlets are GFCI, but if yours is not, plug the extension cord into a portable GFCI adapter first.

Keep the cord away from foot traffic, water pooling, and sharp edges. If the cord must cross a walkway, cover it with a cord protector or cable ramp to prevent tripping and damage. Do not bury the cord or run it through water. Coil excess cord loosely near the outlet rather than leaving it tangled on the ground.

Check the cord and connections before you turn the lights on. Look for cracks, exposed wires, or corrosion. If you see damage, do not use the lights — replace the cord or the string.

Maintain lights through the season

Outdoor lights face sun, rain, wind, and temperature swings. Check them monthly during the season. Look for loose bulbs, corroded sockets, or water inside the string. Tighten any bulbs that have worked loose. If a socket is corroded or a bulb does not light, replace it rather than leaving a dark spot in the string.

After heavy rain or wind, walk the patio and check that the string is still tensioned evenly and that no anchors have shifted. Retighten turnbuckles if needed. If the string sags into a walkway, adjust the tension.

At the end of the season, turn off the lights and let them dry completely before storing them. Coil the string loosely in a dry place, away from extreme heat or cold. Store bulbs in their original packaging if possible. LED strings last much longer than incandescent, so if you are planning to use lights year after year, the upfront cost of LED pays off.

Frequently Asked Questions

Can I use indoor string lights on a patio if I cover them?

No. Indoor lights are not sealed against moisture and will corrode and fail even under a cover. Moisture gets trapped under the cover and speeds up corrosion. Use outdoor-rated lights only — they are designed to handle wet conditions.

How much sag should the string have?

Aim for 2 to 3 inches of sag per 10 feet of span. This is enough to absorb wind and temperature changes without the string dipping into walkways or collecting water. If you are unsure, start loose and tighten gradually until the sag looks right.

What if I do not have a tree or post to attach lights to?

You can install a post or bracket on your patio. A deck post can be bolted to the patio surface or sunk into concrete footings. A wall bracket can be mounted to the house or a fence. Both give you a solid anchor point. Make sure any new structure is rated for outdoor use and properly fastened.

Do LED string lights get hot?

LED lights stay cool to the touch, which makes them safer around plants, fabric, and children. Incandescent bulbs get hot and can burn skin or ignite nearby materials if they touch something flammable. If you have plants or decorations near the lights, LED is the safer choice.

Can I leave string lights on all night?

Yes, but LED lights use far less power and generate less heat than incandescent, so they are cheaper to run overnight. Incandescent lights will shorten the lifespan of the bulbs and increase your electric bill. If you plan to run lights for many hours each day, LED saves money over the season.