How to Keep Squirrels Out of Your Attic

Have you ever tried to outsmart a persistent squirrel? Countless homeowners have bravely taken on this backyard battle. More often than not, the squirrel leaves the homeowner looking about as hapless as Wile E. Coyote in a war of wits with the Road Runner.

The inquisitive creatures are frustratingly adept at using their acrobatic antics to make seemingly impossible long leaps onto bird feeders, sneak into newly planted gardens, or gnaw, squirm, or squeeze their way into attics.

The problem is worse than normal in some regions of the country this year. Parts of the eastern United States, for example, are experiencing what Paul Curtis, an extension wildlife specialist in the Department of Natural Resources at Cornell University in Ithaca, New York, calls a population eruption of the gray squirrel.

“The first sign of the problem was when reports of large numbers of road kills started coming in,” Curtis said. He added that he has also received anecdotal reports of large numbers of squirrels in the lower and central Hudson Valley and in Western Vermont, where they’ve wreaked havoc with fall apple crops.

The problem extends down the coast into the Mid-Atlantic states. George Rambo, a pest management expert and owner of the franchise Critter Control Northern Virginia, says gray squirrels have produced an extra litter this year. Squirrels normally produce two litters a year, one in spring and one in fall. This year they produced a third litter in the summer, Rambo said.

Why So Many Squirrels?

“The population increase is likely caused by really good acorn crops,” Curtis said.

Rambo concurred, adding that the recent mild winter created an environment that led nut trees to produce bumper crops. “Plenty of food encourages animals to increase their populations, he said.

With more squirrels, there’s an increased risk that they will find their way into attics. At this point, they go from being a backyard nuisance to an indoor hazardous pest.

As they search for entry points, squirrels may damage siding, soffits, fascia boards, chimney flashing and even various types of exhaust fans. Once in the attic, they may build nests where they create a mess with droppings and urine. Even worse, they chew through electrical wires in an effort to keep their teeth short, which creates a potential fire hazard, or they destroy furniture or other household contents if they get into living areas.

Homeowners, however, can take heart.

“These population eruptions don’t tend to last long,” Curtis said. “Squirrels have a high mortality rate. Many only live a few months. And, while the past few years have been good for acorns and beechnuts, the forecast is not good for the population eruption to continue.”

Until nature takes care of the problem with a return to more normal winter weather and a drop in nut production, here are some steps homeowners can take to evict and keep squirrels out of their attics. And you do want to take action instead of waiting for them to leave, because they can cause considerable damage.

Check the Trees Near Your House

These tips apply to all trees and branches within jumping distance of the house, which is six to eight feet.

• Prevent squirrels from climbing the tree by fastening a two-foot band of sheet metal around the trunk six to eight feet above ground.
• To fasten the sheet metal, wrap wires around the trunk and attach them together with springs. (The springs will allow the sheet metal to spread as the tree grows.)
• Trim limbs so that the nearest perch is at least six to eight feet from the house.

Inspect the House for Attic Entry Points

Because attics often become too hot in the summer for squirrels to live in, summer is often the best time to block attic entry holes.

Inspect outside: Start by looking at the exterior of your house for any existing places where squirrels may have already entered the attic. Be aware that entry holes may be smaller than you expect. Rambo says a squirrel can get through an opening about the size of an adult fist. Look for gaps and weak areas such as rot during the exterior inspection.

Check inside: Then inspect the interior of the attic. Light shining through from the outside could indicate a point of entry.

Seal entrances: Seal all possible entrances securely and replace rotting wood, but be aware that squirrels can scratch and chew their way in despite your best efforts. Seal openings at joints of siding and overhanging eaves. Seal openings where utility cables or pipes enter buildings.

To seal entrances, securely fasten 1/4-inch or 1/2-inch hardware cloth (available from hardware and box stores) over attic vents, a common entry point. Be sure to use a wire hardware cloth, not a mesh cloth. Extend the hardware cloth 2 inches beyond the hole in all directions. This is a precaution to stop the squirrel from gnawing around it. To secure the hardware cloth, use a staple gun, U nails or regular nails and reenforce with sheet metal screws.

Use a repellent: Spray the area with a proven repellent available at garden, hardware, pet or feed stores. You can buy premixed chemical or natural ones, and the latter usually relies on the scent of predator urine to scare the squirrels away. Apply to wherever the squirrels seem most likely to be, around hole openings or wherever there are traces of their own urine and feces, or where you see tracks. Mothballs are not effective—and are even illegal to use against squirrels in some places.

You can also use a homemade repellent by combining hot sauce and water at the rate of 1 tablespoon of sauce to 1 quart water. Or mix a chopped yellow onion, a chopped jalapeno pepper and 1 tablespoon cayenne pepper, and boil for 20 minutes in two quarts of water. Let cool, strain through a cheesecloth, and apply with a spray bottle. The mixture, which reportedly works against virtually all animals, is only effective for three to five days.

Check chimneys: Install caps on chimneys. Check for gaps in the flashing at the chimney base.

Add bright lights: Install some bright lights in the attic, which are likely to make the squirrels feel vulnerable and exposed, and deter them from wanting to stay. It's even better if you can direct the light right at the nest.

Avoid Trapping a Squirrel in the Attic

If you suspect squirrels have already entered your attic and you have found what appears to be their entry point, don’t accidentally block them inside. To determine whether the squirrels are inside or outside the house, ball up some newspaper and stuff it in the hole. Wait two days. If the newspaper remains intact, there’s a good chance the squirrels are outside. In this case seal the hole.

If the newspaper is pushed away, set a live trap. (These are available from hardware stores.) Cover the trap with a blanket or towel to reduce stress on the animal. Take the trap outside and release the squirrel in your yard near its entry point to the house.

Generally, squirrels leave attics during the warmest parts of the day when an attic becomes uncomfortably hot, so that's the best time to implement any eviction efforts. You're more likely to hear activity in the attic and to encounter squirrels inside during cooler hours and seasons. They tend to be more active at dawn and dusk.

Rambo notes that once a squirrel has been trapped once, it will be difficult to trap again. Also be aware that most states have permit and/or licensing laws and regulations that govern companies that do wildlife work. Jonathan Kays, an extension specialist for Natural Resources in the Western Maryland Research & Education Center at the University of Maryland Extension, points out that it is illegal to trap and transplant wildlife in Maryland without a permit.

Rambo suggests making sure any exterminator you choose is licensed or permitted in nuisance wildlife work and that they show proof of insurance and any warranties that come with the work. In most states, the permit is given to individual technicians and not the company that employs them, he adds.

What If There’s a Nest With Babies in the Attic?

If a squirrel has built a nest in the attic that is not detected until there are babies, there are several options to remove the mother and infants.

Option 1

This requires patience. Wait until the babies have left the nest. This usually tales 12 to 14 weeks. Then seal the entry hole.

Option 2

This requires several steps but gets the mother to remove the babies herself:

1. Locate the nest.
2. Gently use a pole and pull the top off or slide the nest about a foot.
3. Place a radio set to an all-talk station about 6 feet from the nest. It only needs to be loud enough to fill the attic, not the entire house.
4. Toss an ammonia-soaked rag tied with string or fishing line near the nest.
5. Position a bright light so it's shining directly on the nest.
6. The mother will move the babies, usually very quickly if she has an alternate nest site.

Option 3

This requires a phone call ... to an exterminator.

Of course, you can always call an exterminator to begin with rather than go the do-it-yourself route.