Measure the spans properly
Measure from fixing point to fixing point: the eye on the house wall to the post, the post to the bar's fascia, and so on. A tape along the ground under the line gets close enough. Then decide how much droop you want. A taut line looks tidy and puts more load on the fixings; a gentle swag looks relaxed and uses more cable. The droop buttons add that extra length.
Add the lead-in too: the distance from the outdoor socket or transformer position to the first fixing. Many sets have a short lead before the first bulb. If it doesn't reach, move the supply point with an electrician rather than adding an extension lead outdoors.
Use the product's own figures
The spacing between bulbs, the lit length of one set and the number of sets you can link all vary by product. Take them from the listing or the instructions, not from a different set you liked the look of. The linking limit matters: exceed it and you may overload the transformer or the first set's cable.
Safety outside
- Check every IP rating. Bulbs, cable, connectors and the transformer can have different ratings, and the transformer is often indoor-only. See festoon lights and IP ratings.
- Use RCD protection for outdoor electrical equipment, as Electrical Safety First advises.
- Support the cable. On longer spans, a catenary wire takes the weight off the light cable.
- Keep connections off the ground and out of the path of a hose or rain run-off.
Fixed outdoor wiring is a job for a competent electrician; our power guide explains the planning.
Beyond festoons
Festoons give atmosphere, not task light. A bar also needs a light you can pour and wash up by, and safe lighting on steps and paths. See the lighting guide, and for spots far from the house, solar power for a garden bar.
Next step
Once the count is settled, add the lighting line to the budget planner and sketch where the supply point will go before you talk to an electrician.
Quick answers
How much droop should festoon lights have?
It is a look as much as a measurement. A gentle swag usually looks best and is kinder to fixings than a drum-tight line. Pick an allowance in the planner and check it with string before buying.
Can I link different festoon sets together?
Only if the maker says they are compatible, and only up to the stated number of sets. Mixing products can overload the transformer or the cable.
Can festoon lights stay up all winter?
Some are designed for it and some are not. Check the instructions, and inspect cables, connectors and fixings each spring. See festoon lights and IP ratings.
Sources
Primary guidance checked 10 November 2026.