Examine the house for obvious entry and exit points. Some squirrels will find an inch-wide opening in the outside walls, siding, or roof, and chew on the material in order to make it bigger. The most common points of entry for squirrels are the roof and outside vents, which lead to the attic. The entry holes should be closed off immediately once they have been located.
Seal the openings the squirrels created in the roofing material. Fortify the repair with steel. This will prevent the squirrels from chewing through it again. Check for other soft spots in the roof to further prevent them from entering. Close off any open pipes in the attic.
Install a one-way entry trap in the main entry hole to your house once all the other openings have been sealed. Most squirrels leave the nest on several occasions to gather food or water outside. The trap will allow the squirrels to exit; the reinforced door inside it will not allow them to return.
Forced removal is the only proven way to rid the building of squirrels. Moth balls do not force them to leave, and rat poison or pesticides do not harm them. In most cases, the squirrels avoid these things entirely.