How Common Household Pests Get In
Although your walls may appear solid, many walls are full of tiny pest passageways. Small insects can sneak through the tiniest cracks, so you may not be able to make your home absolutely bug-proof. But you can seal most gaps, especially the larger ones that let in mice and larger insects. Put on some old clothes, as you'll have to get on the ground, slink behind bushes and even crawl under your deck to examine your home's exterior. Take a flashlight and a mirror along. If mice are your main concern, also bring a pencil. If you can slide the pencil into a crack, it's large enough for a young mouse to squeeze through. Take your time and examine every square foot of your home. The key areas to inspect include wall penetrations, doors and windows, the foundation, dryer vents, exhaust fans and roof vents.
Plug Gaps With Mesh
Stuff in a generous amount of copper mesh with a screwdriver, leaving about half an inch of space for expanding foam sealant. Seal gaps with foam.
Protect Wood From Moisture
Insects and other small pests need to draw life-sustaining moisture from their surroundings, so they avoid dry places and are attracted to moist ones. If the soil around your house, the foundation and the walls is dry, it'll be less attractive to insects, spiders and centipedes. Rake moisture-wicking soil and mulch away from the window frames and low wood. Turn your mulch periodically to help keep dampness down, and keep bushes trimmed back as well.