Schwandner received his doctorate in 1975 from the Technischen Universität München (Germany) with a thesis on the older temple of Aphaia on Aegina (German title: Der Ältere Tempel der Aphaia auf Aegina) under the supervision of Gottfried Gruben. Until his retirement in 2004, Schwandner held the post of director in the architecture department of the German Archaeological Institute (federal German archeological survey) in Berlin. In 2002 he joined the faculty at the Winkelmann Institute of the Humboldt UniversityBerlin as adjunct professor ("Honorarprofessor"). Schwandner's research primarily focused on the architectural history of ancient Greek architecture.