Bats commonly enter buildings through the overhang of the roof made by overlapping sheeting or drop siding. They are most often found in attics, between roofs and ceilings or roof spaces, in cornices, fascias, or other crevices around the roof, in walls, in chimneys, around drainpipes, behind rafters and sheathing in open barns, between a window and screen, and occasionally in crawl spaces. Depending on the size of the space and on the species, bats will be found singly, congregated in groups of a few individuals, or in colonies of hundreds and occasionally thousands. The accompanying odor can be pungent but not dangerous. They are most likely to cause a nuisance after a house has been batproofed, thereby ridding the edifice of bats but leaving arthropods.
Ectoparasites quickly die in the absence of bats.
Some bats temporarily roost behind shutters, under wood shingle siding and roofing, roof gutters, awnings, trim with overhang, under flashing around chimneys which has separated or loosened from the solid structure, open garages, patios, porches, breezeways, open livestock shelters, and under sheets of tarpaper. Shutters on brick houses are especially attractive as day roosts for transient bats in migration and for males that frequently take refuge behind shutters during the nursing season. In exceptionally hot weather, individuals may abandon an attic and reside behind shutters. Big brown bats are partial to roosting behind the trim below roofs of houses. Unusual roosting areas include sewers, wells, and graveyard crypts.