The facade of the mid-20th century District Health Center No. 1 building at 500 S. Broad St. has been added to the city's Register of Historic Places, potentially complicating efforts to redevelop the property after it is vacated before the end of next year.

The Philadelphia Historical Commission's historical designation committee named the three-story building's glazed-brick exterior to the register at a meeting Friday, according to a release from the Preservation Alliance of Greater Philadelphia, which nominated the property for the list.

"Remarkably, more than 50 years later, District Health Center One today retains its original use as a clinic, central office and laboratory for Philadelphia's Department of Public Health," the group's advocacy director, Patrick Grossi, said in a release. "It is a testament to the planning and ambitions of the system's mid-20th century overseers."

The designation applies to the city-owned structure's "entire building envelope," though not its interior, Preservation Alliance executive director Paul Steinke said in an interview.

Health department officials have said the building's current functions, which include a medical lab and a clinic for sexually transmitted diseases, are to be consolidated at other locations by the end of 2018.

The Philadelphia Industrial Development Corp. has begun vetting development proposals from bidders on the property for the city's Department of Public Property. In most cases, developers seeking to alter structures listed on the city's historic register must prove to the Historical Commission that preserving the properties would represent a "hardship" preventing their profitable use.

Public Property Department spokesman Mike Dunn said the administration does not oppose the historic designation and "will continue to pursue a quality reuse for the property in keeping with the best interests of the city."