Squirrels living in attics are a concern because they may gnaw on boards and electrical wires. Usually, the most serious problems come from nesting adult females. They often build their nests near openings, such as an unscreened vent or loose or rotten trim boards.
The first sign of a squirrel in the attic is usually the sound of scampering during the day, as they come and go on foraging trips. Juvenile squirrels, and sometimes adults, may fall into wall cavities and be unable to climb out, making persistent scratching noises as they try to escape (and eventually dying if they can’t).
Here's what to do if you've got squirrels in your attic:
Find the point of entry. Thoroughly inspect the inside of the attic to find the opening(s). If there is no way into the attic, inspect the exterior eaves, vents and roof.
Find out if it's a mother squirrel with young. Try to locate her nest (probably made of readily available materials like insulation, cardboard and leaves). If it's February through May or August through October, you can be sure that babies are present. In that case, the best thing to do is wait a few weeks until the babies grow old enough to leave with their mother—they won't survive without her. Don’t try to trap and relocate the family yourself.
Get them out. If you can't wait until the mother and babies leave on their own, hire a professional who knows how to reunite mothers with their offspring. If you find the nest and there are no baby squirrels, you can try to frighten the adult squirrels into leaving. It might be as easy as banging on the rafters or going into the attic and speaking loudly. You can also try putting a bright light in the attic and leaving it on, playing a radio around the clock or putting rags soaked with cider vinegar in the attic (squirrels don't like the smell). Or you can just wait until you’re sure all the squirrels have left, which they usually do during the day.
Keep them out. We recommend installing metal flashing to keep squirrels from re-opening access points into attics. Often, they will attempt to get back in anyway, and this can be a signal that young are trapped inside.
Listen carefully after excluding to be sure no squirrel is trapped inside or has gotten back in. Watch closely to see if the squirrel keeps trying to get back inside. Mothers will go to extremes to get back to their babies and frantic attempts to reenter are usually strong evidence that young are still inside. In this case, remove the patch, let the mother return and watch to see if she moves the litter. If it's really cold out, it's best to wait until spring before removing the squirrels. Excluding them in the depth of winter might compromise their survival.
Squirrels who have been in attics for a while may have chewed on exposed wiring, which might cause a fire. Once they are gone, ask an electrician to closely inspect all exposed wiring.
Beyond the attic
In tight places, such as crawl spaces between floors, try snaking a vacuum cleaner hose into the restricted space. Reverse the setting to blow air and leave the vacuum on until the nester leaves to seek more pleasant digs.
When to call a professional
If you need to evict a mother and her babies or if you're unable to get the squirrels out on your own, we strongly recommend hiring professional assistance. Evicting squirrels can be difficult. There are potential safely risks to the homeowner and humane concerns for the squirrels if the eviction isn’t done properly.
Relocation is not the answer
Live-trapping squirrels and taking them to "the woods," where they will live happily ever after, is not the ideal solution to local problems. Studies show that few squirrels may survive the move. And when a squirrel is removed from a yard, another squirrel will move in, sometimes within a few days.
Public health concerns?
Squirrels can harbor pathogens (such as salmonella) that may be harmful to people, but transmission has rarely, if ever, been documented. And although rabies can occur in squirrels, as in any mammal, there is no documented case of any person getting rabies from a squirrel.