Why are there suddenly so many spiders in my house?

Online Answer
Having a lot of spiders in your house means that the spiders are finding a regular food supply. Since spiders eat insects, that means that there are insects in your house. If there are enough insects to feed a large spider population, it means that there's a large insect population in your house as well.
Related Questions 📌
Eucalyptus, tea-tree or even peppermint oils might keep the spiders out. While some might enjoy the smell, the spiders do not. Spray around windows and doors. A similar option is vinegar.
The story goes that conkers contain a noxious chemical that repels spiders but no-one's ever been able to scientifically prove it. There's hearsay that if a spider gets close to a conker it will curl its legs up and die within one day. Others say spiders will happily crawl over conkers with no ill effects at all.
Vinegar: Mix equal parts white vinegar and water in a spray bottle and spray it directly onto any spiders you see. Vinegar contains acetic acid which burns the spider upon contact..
A corner provides attachment points with some air between them. Imagine a spider building a web in the middle of a blank wall. The web would end up lying flat on the wall, which is not very useful for catching flying insects..
Leaving lights on when it's dark: Just like a bear that is attracted to a flowing river filled with jumping fish, spiders are attracted to bright lights, surrounded by flying insects. Any place that is near an insect-attracting light is prime real estate for spiders.