Spiders prefer quiet, dark and undisturbed areas, including attics. Most spiders are harmless and, in fact, are beneficial because they prey on flies and other undesirable insects. Nevertheless, many people are frightened of spiders and thus may want to kill those living under their roof. Fortunately, you have several ways to do this depending on the level of infestation.
Remove spiders, webs and egg sacs in your attic using a vacuum cleaner. A thorough inspection of cracks, corners and other dark, undisturbed areas with a bright flashlight will help you locate spiders, webs and egg sacs.
Spread an insecticide around the perimeter of your attic. Insecticides that effectively kill spiders include carbaryl, bendiocarb, chlorpyrifos or any of the synthetic pyrethroids, such as cypermethrin, cyfluthrin and lambda-cyhalothrin. As a natural alternative, place sticky traps around the perimeter of your attic.
Bug bomb your attic. Bug bombs, also called insect foggers, are cans of pesticides that spray out all at once. Be sure that the bug bomb you use is labeled for home use to kill spiders. Moreover, be sure to follow the instructions and warnings on the package, as bug bombs can be extremely dangerous.
Hire a professional. Pest exterminators are trained to remove spiders from homes.