The mishap took place early on Tuesday at Raikhola, said Shah Ali police OC Md Anwar Hossain.
He identified the deceased as Kulsum Aktar Nishi, 15, a ninth grader at a local school.
The two-storey building that used to be a shelter home was declared abandoned a few years back.
However, two families had erected a tin-shed house beside it and had been living there for quite some time, said the OC.
“Portions of the rooftop and a wall of the dilapidated building collapsed on the tin-shed, injuring Nishi and her younger brother Raihan in the early hours,” he said.
The two were taken to Dhaka Medical College Hospital, where doctors pronounced Nishi dead.
Raihan, 9, was released after being given first aid.
Eight members of the two families used to live in the tin-shed. The others had managed to evade the accident, said OC Hossain.