Kernrechtsfrage
Whether the later introduction of commercial use for the room is a permit-requiring change of purpose.
Extrahierter Entscheid
Yes. Because the room had not been approved as commercially used, the later commercial use constituted a material change of purpose requiring a building application.
Extrahierte Begründung
The decisive point was not any prior de facto use by former owners, but whether commercial use had ever been approved. The original plans and area calculation showed the room was not treated as a commercial area.