Rooftop office

Rooftop office

CROSS Architecture

Benthem Crouwel Architects
Aachen, Germany
Project Year
© Jens Kirchner

Rooftop office

CROSS Architecture as Architects

Urban redensification in Germany: Prismatic cubature for elegant office construction in Aachen

With the Rooftop Office, CROSS Architecture has created a prismatic building structure for the renowned furnishing house Mathes in the middle of Aachen, which not only opens up unique perspectives on the cathedral and the old town, but also brings working in the Open Space Office to a new level. In addition, the project provides a positive impulse with regard to the redensification of urban areas. Mid-sized town Aachen (Aix-la-Chapelle) ist he westernmost city in Germany.


CROSS Architecture has given the 1960s existing building a progressive look with a 400 sqm prismatic structure. "This building needed an extraordinary architecture that was appropriate to the particularity of the location," explains Markus Sporer, Founding Partner CROSS Architecture. The result is a structure with a trapezoidal basic figure that is created by the play of differently inclined window and façade fronts - tilted outwards on the cathedral side and inwards on the other sides. There is a terrace all around. The cubature is derived from the urban planning situation in the immediate vicinity of the World Heritage Site Aachen Cathedral and Town Hall, the consideration of lines of sight and orientation.


Hybrid construction

It was not possible to continue constructing the existing building in an upward alignment. In order to comply with the urban planning spacing requirements in the old town, which is characterised by narrow lanes, and since the load-bearing columns of the existing building are offset 1.50 to 2.00 metres from the façade to the inside, CROSS installed a pointsupported girder grid for the new façade extension. This has resulted in a circulation that offers new qualities - for use as a fringe terrace for the new office. The project is designed as a hybrid construction in steel/wood construction in order to achieve a short construction time with high economic efficiency through prefabrication. The innovative extension, which was developed in an integral process, also made it possible to realise the project with minimal impact on the underlying shop use.


Inspired by luxury yachts

The eaves of the superstructure are set inwards on the south and east sides, which provide a view of the entire building from a distance. On the west side, the eaves are deliberately pulled forward so that the figure is clearly oriented towards the cathedral and can also be seen from the alleys. - Markus Sporer: "This orientation towards the cathedral also offers a cool effect for the interior.“


Thus the trapezoidal solution for the superstructure was derived from the process - in harmony with the architectural and urban requirements - as a matter of course. The completion of the sleek looking futuristic figure with its extreme angularity and shimmering facade in elegant grey, realised with Alucobond panels, is inspired by luxury yachts. An aesthetic that CROSS appreciates.


Dark colour code: Staging of the view

Generousness is also evident in the interior. Not only through the window fronts on all sides. The play with different room heights creates the desired volume: while the height directly on the facade is 2.50 metres, it rises to 3.30 metres towards the centre of the structure. A roof inclined downwards thus sets accents here. The interior is marked by an almost black, deep grey ceiling in combination with oak parquet on the floor - a warm aesthetic for a modern, open office landscape, which Mathes has now moved into with his creative and planning team. "The interior creates the feeling of a protected space," explains Markus Sporer. In addition, the consistently dark colour coding of the ceiling stages the moment of a view, similar to the effect of a passe-partout.


Because an open office landscape without partitions was to be created in the superstructure - also so that the axes of vision in all directions remained free - the subject of acoustics came to the fore. CROSS found the optimum solution by using aluminium slats. 90% of the available ceiling areas could thus be occupied acoustically. A cost-effective variant that would not have been possible here with almost any other material. In addition, the dark slats offer an aesthetic benefit: the profile structure produces shades that make the entire ceiling appear even darker.


The natural ventilation also offers a high level of comfort for working in the new work space: all windows can be folded outwards in a charming way. In the centre of the room, there is also a skylight that can be opened. It supplies the modern office landscape with additional daylight and fresh air.

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