Find and seal entry points
The first step you need to do is make sure the squirrel only has on exit out of your attic. This means you need to find every possible hole the squirrel can use to exit and enter your attic.
Once you find the holes, you must seal them. Use caulk, foam insulation, mesh wiring, or wooden boards to cover the holes. Keep in mind that squirrels are experts at chewing and can even chew through soft metals, so make sure that the holes are reinforced strongly.
Leave one hole unsealed, as in the next step you’ll be using it as the squirrel’s only exit point.
Apply a one-way door
If a squirrel or squirrels remain in your attic, you need to create a hole for them to leave, but not to enter again. This can be accomplished using a wire mesh or thin sheet of metal.
Take the material and create a funnel shape, one end big enough to fit the hole, and the other end narrow enough for a squirrel to squeeze through. The whole funnel should be about 12-16 inches in length.
Once the one-way exit is created, squirrels will be able to leave but not enter. You can speed up the process of squirrel removal by using deterrents such as chemical repellents and noise.
Use a deterrent
Buy a chemical repellent and spray your attic. This will cause an unpleasant sensation for squirrels, causing them to flee sooner. Keep in mind this can also cause your attic to be stinky or filled with chemicals, too.
You can also use noise such as radio to cause squirrels to consider moving homes. However, it is best to get professional advice in the long run, as professional wildlife companies will often know the best ways to get squirrels out of your attic.