As the title already suggests this project aims on densifying existing urban space. It is therefore a part of the urban policy to provideattractive and central living space in a city that has become always more important as a connection between west- and east europe sincethe fall of the iron courtain. This policy certainly contributet to Vienna again being chosen as the city most worth living in by the mercerstudy2010. The roof extension was added in 2008 on the top of a residential building in Vienna out of the turn of the century. In the cornertwo different motions of the roof engage and the spatial mesh forms a new architecture which has the significance of a landmark forthe sorrounding area. The terraces are closely connected to the living area. The concept is built upon the idea of an open floor plan. Thedifferent living areas are formed by spatial arrangement.