Public Safety officials said East Carson Street between 10th and 12th streets will be closed overnight.
Officials said the building, located in the 1100 block of East Carson Street, is considered structurally unsound by the Department of Permits, Licenses and Inspections.
Public Safety Director Wendell Hissrich said the building will be demolished on Tuesday if it doesn’t come down on its own Monday night.
Pittsburgh fire Chief Darryl Jones said no one was injured in the fire and no one is missing. The cause of the fire is under investigation.
The building was home to the South Side Chamber of Commerce offices, a barbershop and six apartments.