How to keep spiders out of the house

Most of them are useful

Worth saying plainly: the great majority of spiders in and around a New Zealand house are harmless and actively helpful, eating the insects you'd otherwise be dealing with. The goal is usually keeping numbers and webbing manageable rather than eliminating them.

Exterior first

Spiders sit where the food is, which is around lights, in sheltered corners and along eaves. Treating the outside of the building - eaves, window and door frames, under the guttering, sheltered corners - deals with them where they actually live.

Timing matters more than product. A treatment applied at the wrong point in the season does considerably less.

Turn the lights down

Outdoor lighting draws moths and flying insects, which draws spiders. Warmer-toned or lower outdoor lights, or simply using them less, reduces the food supply - which is a more durable fix than spraying.

White-tailed spiders: the honest version

White-tailed spiders can give a painful bite causing local redness and swelling, and some people react more than others. The widely repeated claim that they cause flesh-eating ulcers is not supported by the research - a study of confirmed white-tail bites found no cases of necrotic ulceration. Worth knowing before anyone panics.

Clear the webbing

Knocking down existing webbing matters for a practical reason beyond tidiness: a cleared surface makes it obvious whether treatment is holding, because new webbing is easy to spot.