The girl was on the roof of the Mohawk Electric Construction Co. late Thursday afternoon when she stepped onto a brittle plastic skylight, the Chicago Tribune reported.
A 13-year-old boy on the roof with her called his father, who called 911, said police.
The girl was able to get to the front door and unlock it for emergency workers.
She reported pain in her neck and back and a minor cut on her arm, police said.
Fire officials said she was in serious condition with trauma injuries when she taken to the hospital, where police said her condition had stabilized.