A purpose-built thing was designed and made for that job from the first drawing, not changed later to fit. A purpose-built hospital is a hospital they planned as a hospital, not a warehouse they later filled with beds. A purpose-built studio is made for recording, not a spare room with blankets on the walls. The important piece is “from the start.” If they took an old building and fitted it to a new use, that is converted, not purpose-built. The word is especially at home in British English; American speakers more often say built for or designed for. You will see it on buildings, rooms, tools, and vehicles. It is practical, not emotional.