栋 (dòng) is the classifier for standalone buildings like houses, villas, and office blocks — it emphasizes the physical structure as a unit. 座 (zuò) is used for larger or more imposing structures (mountains, bridges, towers) and can also be used for buildings but often implies grandeur. 所 (suǒ) is for buildings as institutions (schools, hospitals, police stations), focusing on function rather than the building itself.