WHAT TO LOOK FOR
Raccoons are able to gain entry through just about any common building material (e.g. wood, soffit, aluminum flashing, shingles, attic, and roof vents. Raccoons emit a large number of vocalizations and prefer to build dens in warm, dry locations such as attics or crawlspaces.
They are very active animals and will scurry around attics, chimneys, and roofs, usually at night. Feces and fur are often found at the entry point and there can be a strong odor detected. Raccoons tend to leave feces piles on roofs and their elongated rear foot leaves a distinctive footprint.
The most effective method is to remove all the raccoons and completely seal the entire building from further entry. If there are unweaned young present they need to be removed from the nesting site as soon as possible after the female is captured. If raccoons are living in a crawlspace or attic the amount of damage they can cause to insulation and ductwork can be quite severe. If the damage is accessible, then your property insurance may cover the cost of the damage repair and raccoon removal.