The existing office building of Viereck Architects in Graz was expanded with a monolithic building volume, creating a balanced architectural ensemble. Large glass surfaces define the building’s character and provide light-filled interiors, while the glazed atrium between the existing and new structures creates a seamless connection. The façade, clad in aluminum composite panels, gives the building a modern, monolithic appearance. Both buildings were constructed using timber construction methods, supporting a sustainable approach to building. Inside, warm, tactile surfaces and natural materials such as wood, stone, fabric, and glass create a harmonious atmosphere. Exposed and polished concrete surfaces add a touch of industrial elegance. An elegant color palette of gray, white, and black, accented with shades of green, red, and brown, contributes to a welcoming and comfortable environment. Acoustic elements made from recycled materials enhance the indoor acoustic quality. Heating is provided by an air-source heat pump and underfloor heating system. Sustainability is further supported by a photovoltaic system, heat recovery technology, and intelligent building management controls.