Rem Koolhaas' firm has revealed plans to overhaul continental Europe's largest department store, with the addition of a glass rooftop extension and a series of sculptural new staircases (+ slideshow).

Rotterdam-based OMA has been charged with renovating and extending Berlin's Kaufhaus des Westens, more commonly known as KaDeWe – a century-old building with 60,000 square metres of retail space.

The firm's approach will be to treat the structure as four connected shops, each with its own entrance and circulation spaces. The aim is for each "quadrant" to have its own identity.

OMA describes its proposal as a tactical response to "accelerating shifts in consumer behaviour and the challenges brought by online retail".

"The new components fragment the original mass into smaller, easily accessible and navigable components – similar to distinct urban sectors embedded into a unified city fabric," it said.

The glazed rooftop extension will span two of these quadrants, replacing the vaulted restaurant that currently forms the top of the building. It will create a new ninth floor of retail, and will slightly alter the profile of the existing structure.

Two new elevators will create a direct link between this additional level and the street below.

"The particular configuration of the new rooftop leaves an open-air courtyard between the new architectural insert and the rest of the building," said the architects.

"The resulting irregularly shaped courtyard provides a space for outdoor programmes, and unveils simultaneously the most exciting and yet most secret spaces of KaDeWe."

Kaufhaus des Westens first opened in 1907 and has experienced numerous renovations over the years, the most recent being an arched glass ceiling that was added in the 1990s.

The landmark store was referenced by David Bowie in the 2013 track Where Are We Now? In the song the musician, who died last week, reminisces about Berlin, where he lived between 1976 and 1979. At that time the store was a potent symbol of Western luxury and was the place many East Germans headed for first when the Berlin Wall came down in 1989.

Internally, OMA's renovation will centre around creating the four new staircase atriums. Each atrium will have a different shape, and the cuts through the existing floorplates will vary on each level to make every space unique.

"Through a process closer to the one of curating rather than designing, each void is developed specifically to offer four kinds of distinct spatial experiences and four efficient models of organisation," said OMA.

OMA's KaDeWe project is the latest in a series of planned renovations at some of Europe's most important department stores. David Chipperfield has been appointed to overhaul London's Selfridges, while SANAA has been working on the development of La Samaritaine in Paris.

Koolhaas' firm is also working on a new department store that will occupy a converted Venice palazzo, and is transforming a 19th-century structure in Paris into a gallery and art studio for department store Galeries Lafayette.

Renderings are courtesy of OMA.