How to Hang String Lights Safely Outdoors

Outdoor string lights add ambiance to a deck or backyard, but a poor installation — wrong extension cord, inadequate support, or exposed connections — creates a shock or fire risk. Here’s how to hang string lights safely and to code in Ontario.

Use outdoor-rated lights and cords

The most important rule: use lights and extension cords rated for outdoor use. Outdoor-rated products are marked with a weatherproof symbol (W or WW) or “for outdoor use” on the packaging. Indoor-rated extension cords have thinner insulation that degrades in UV, moisture, and temperature swings — Ontario’s freeze-thaw cycles accelerate this damage. Never daisy-chain more than three extension cord sets; each connection is a potential fault point exposed to weather.

GFCI protection is required

Ontario’s Electrical Code requires outdoor receptacles to be GFCI-protected. If you’re plugging into an existing outdoor outlet, it should already be GFCI-protected (look for the test/reset buttons on the receptacle face). If your outdoor outlets don’t have GFCI protection, install a GFCI receptacle or use a GFCI-protected extension cord before plugging in any string lights. GFCI protection trips within milliseconds if moisture enters a connection — it’s the main safety mechanism for outdoor electrical use.

Supporting the lights: catenary wire and anchor points

String lights are not structural cable. For spans longer than 3 metres, support the lights with a catenary wire — a stainless steel cable run between anchor points (eye bolts into joists or structural posts). Drape the string lights over the catenary wire rather than using the light wire itself to carry the load. This prevents sag, reduces connector stress, and extends the life of the strand. For shorter spans, screw-in cup hooks in wood framing work well. Never nail through the wire insulation to attach lights to a surface.

Protecting connections from weather

Extension cord connections and bulb sockets exposed to rain are the most common failure point. Use weatherproof cord covers or outdoor-rated cord connect boxes at each junction. Where a plug-to-extension connection will sit on a surface, raise it off the ground with a small block so it isn’t sitting in standing water. Rubber or silicone socket covers protect individual bulb sockets from water ingress in wet climates.

Expert tip

The most reliable outdoor string light setup we’ve seen is LED strings on a catenary wire, plugged into a GFCI outlet controlled by a smart plug with a dusk-to-dawn schedule. No timer to reprogram seasonally, no power left on during the day, and the smart plug can be controlled remotely. For a permanent backyard installation, running a dedicated GFCI circuit to the outdoor receptacle — instead of using a long extension cord — gives a cleaner result and eliminates the tripping hazard of a cord across the yard.

Contact us

Need a dedicated outdoor circuit for string lights or holiday lighting? Call us at 416-838-9006 or visit our contact page — we install outdoor lighting circuits across the GTA.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp