City solicitor Dan Regan says he plans Tuesday to appeal a county judge's order Monday that would let St. Nicholas Parish demolish the building along Route 28.
The Diocese of Pittsburgh and the parish, which now meets in another building, say the old church closed in 2004 and costs too much to maintain. But Regan, representing the city's Historic Review Commission, wants the building preserved because it's believed to be the first Croatian Catholic church in the United States.
Church officials claim the building is unstable and unsafe.
But the city wants a local civic group to buy the church for $1 to turn it into a museum on immigration.