If you build it, mice will come. Sooner or later, you'll probably need to get rid of mice or rats. Fall is prime time for an increase in mice in your house, as they look for winter protection, but mice and rats can move in at any time. While small, mice and rats can cause big problems. They chew on everything, causing property damage and potential fire risks when they gnaw on electrical wiring and build tinder dry nests in dark corners.