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How Animals Are Getting Into Your House

Some people might as well hang a "vacancy" sign on the lawn. Don't be one of them. Part of How to Keep Pests Out of Your House, a TOH Fall-upkeep series

Photo by Mark Hooper

Common Criminals

This trio of rodents accounts for 80 percent of animal break-ins.


Diameter of entry hole: ¼ inch or larger.

Likely entry points: Garage, basement, gaps around utility lines.

Signs of infestation: 1⁄8-inch-long droppings; smell of urine; noises at night; holes gnawed in food boxes.

Best spots for traps: Along walls; anywhere you suspect activity.

Preventive measures: Seal exterior gaps with mortar; weatherstrip the bottom of basement and garage doors; keep all foodstuffs in hard plastic, glass, or steel containers.

Stopgap measures: Stuff copper mesh or bronze wool into foundation cracks.

Job for a pro?: Probably not, but a large breeding population might require professional backup.


Diameter of entry hole: ¾ inch or larger.

Likely entry points: Garages, basements, rotted sills or foundations, damaged or unused drain pipes.

Signs of infestation: Black, greasy smudges around openings; smell of urine; ¼- to 5⁄8-inch-long droppings; nests of discarded food; fur; matted-down insulation; gnawing and squeaking at night.

Best spots for traps: Poisoned bait stations outside the house and around the perimeter of the property line.

Preventive measures: Eliminate all water and food sources around the house, including bird feeders and pet dishes; store food (pet and human) in airtight containers.

Stopgap measures: Cover entry points with hardware cloth or 16-gauge steel flashing.

Job for a pro?: Definitely.


Diameter of entry hole: 2 ½ inches or larger.

Likely entry points: Where dormers meet roofs or where roof shingles overhang fascia boards. (The second-story men of household pests, squirrels can jump 10 to 12 feet through the air.)

Signs of infestation: Scampering noises in ceilings or attic; insulation missing from spots near eaves; ½- to 1-inch-long droppings; piles of nuts.

Best spots for traps: Live traps, clamped in place near the spot on the roof where they're getting in. Bait them with peanut butter, dried corn-on-the-cob, or suet.

Preventive measures: Prune trees away from house; keep roof and exterior trim in pristine repair; remove bird feeders.

Stopgap measures: Nail hardware cloth over potential entry points until they can be repaired.

Job for a pro?: You bet. Squirrels can carry rabies. Plus, it's tricky climbing ladders with traps, clamps, and jar of Jif.

Illustration by Jameson Simpson

Tempting Home Targets

Unwanted critters can get in through the chimney flue, roof joints, attic vents, pipes and conduit, dryer vents, foundation joints, and wood trim.

Occasional Visitors

Depending on where you live, you may get a drop-in (or burrow-in or slither-in) visit from one of these:

Skunks: These four-legged stink bombs will easily burrow under your patio slab or stake out territory in your garage, crawl space, or basement. Hire a pro to trap them live and transport them elsewhere.

Bats: Given the opportunity, they'll happily take up residence in your attic for the summer and leave behind potentially disease-ridden guano as a present. Seal off their entranceways with a double layer of insect screen and hardware cloth, but only after you evict them first (Bat species are protected nationwide). Call in a pro to erect a "bat flap," a layer of screen that lets the bats crawl out but blocks their way back in.

Birds: In spring, starlings and sparrows have a knack for building nests in hidden, difficult-to-reach openings in a house. The louvered vents for dryer exhausts and the openings behind roof fascia are perennial favorites. Bar them from entering with hardware cloth. Take down the bird feeders that are attracting them to your property.

Raccoons: The masked marauders of the animal world, they'll barge down chimneys and into open garages or attic vents. Best captured with a live trap baited with peanut butter, suet, raw eggs, or dried corn on the cob. To keep them from coming back, cap your chimney, keep basement and garage doors closed, eliminate bird feeders and outdoor pet bowls, and lock down trash lids with bungee cords.

Snakes: In the fall, they'll work their way into openings around basement doors or cracks in foundation mortar, looking for a place to hibernate. They'll leave of their own accord when the weather warms up in spring. Seal those openings behind them.

Opossums: You'll occasionally find these nocturnal fruit-and-insect eaters camped out under your deck or blundering into open garages, basements, and crawl spaces. They won't stay, unless they think you're going to feed them. As with skunks, you'll need a pro to capture them and ferry them out of the neighborhood.

Check out some of our best pest control resources to keep rodents out of your home.