Sammlung Boros – Collection and Residence:
Conversion and extension of an Air raid Bunker in Berlin for the Collection of contemporary art
and living spaces for the art collector Christian Boros and his family by Realarchitektur.
Project description and location
A 5 storey bunker in the centre of Berlin has been refurbished and converted to house the contemporary art collection of Christian Boros. The World War Two building houses approximately 3000m² of exhibition space. Temporary exhibitions in close cooperation with the artists are planned. A 500m² extension at roof level provides living space for the art collector and his family.
Inside the bunker new spaces have been created mainly by subtraction from the existing forms. On top of the building structures are being added which relate closely to existing ones inside the bunker. The two are joined by a connecting piece (staircase and lift). It has been our aim to work with discovered circumstances, to develop out of the existing.
The air raid bunker was constructed in reinforced concrete in 1942 during the second world war, for the German railway company. It was used to protect travellers arriving at the Friedrichstrasse Railway station from air raid attacks. The building is listed by cultural Heritage. It was originally based on the model plans of the architect Karl Bonatz. A similar bunker, that was taken down in 1947, had been erected next to the Schlesischer Bahnhof Railway Station (now Ostbahnhof). The Building was functionally well laid out and could house up to 3000 seated people distributed on five floors. The inner spatial structure has an axially symmetrical layout, that is surrounded by a 1,8 meter thick outer concrete wall and a 3 meter thick concrete ceiling. The free standing
building was build on the corner of a city block in the Mitte district in the centre of Berlin. The four identical facades made of raw concrete are inspired by classical architecture and accentuated by fine details. Double entrances are located on all four sides, connected to intertwined double stairs that enabled many people to enter the building quickly simultaneously.
After the war minor additions and changes were made to the bunker for it to be used as a vegetable storage space. After the Berlin Wall fell it was used as a club and later on for temporary exhibitions. In the year 2003 Christain Boros bought the bunker and commissioned Realarchitektur to design a place for him and his family to live in and house his collection of contemporary art.
The existing spaces seemed appropriate to be used by the art and artists represented in the collection. On each of the five floors a route connects the eight major rooms and the surrounding sub spaces.
The strict symmetry and uniformity of all spaces created a general feeling of disorientation. The building was separated from its urban context by post war additions such as walls, loading bays, an elevator tower and outhouses.
Refurbishment and conversion
Additions, walls and fences were removed. The facades were cleaned and have been structurally refurbished in accordance with the Heritage. The many traces and marks left by the war and the history following, were dealt with individually and partly directly on site. No final cover up screed has been made. The traces remain physically present.
The entrance for the art collection is set on Reinhardstrasse and the private rooms are entered on the park side. To connect up to the newly created dwelling on top of the building, around 150 cubic metres of reinforced concrete were cut out of the bunker's three meter thick roof. The apartment is reached through this opening by way of a steel staircase of meshed steel and an internal open lift, which is partly clad in the same material. The traces of the cut showing old reinforcement bars in the walls and the surfaces resulting from different demolition methods have been left exposed.
The exhibition spaces
Selected ceilings and walls were cut out with a diamond-toothed saw and removed. The resulting overlapping spaces now join the floors vertically throughout. A route runs through the building on every floor around the central core of spaces. In some of these spaces the existing ceiling height of 2,3 meters has been kept and some new spaces now have up to a triple ceiling height of 7,5 meters. The corner rooms have partly been connected horizontally as well as vertically creating diverse complex spaces. The bunker itself now has approximately 80 rooms distributed over 5 floors.
In close cooperation with the artists represented in the collection and the client Christian Boros each space is looked at individually. In addition to the traditional so called white cube spaces, where part of the existing collection will be shown, a structural and spatial interaction between art and architecture has taken place. Now that the rooms have been opened and connected vertically the art can be taken in from different floors and angles and will support the orientation within the building.
Only parts of the walls will be plastered. The diverse surfaces of the concrete walls, ceilings and floors and traces of the buildings history will remain visible.
Materials and spatial motives as found were interpreted and incorporated in the planning of the new living spaces.
Like the bunker itself the new floor is encased on all sides by a homogenous facade. It is build up in several layers consisting of curtains, steel, glass and screens. The glass facade allows in contrast to the thick concrete walls of the bunker views over the surrounding cityscape. The reinforced concrete roof is square and measures 26 meters, its outline corresponds to the inside of the outer walls below. It is supported almost entirely without columns, resting on the internal walls and the supporting glass facade.
On the south and west the line the glass is set back from the edge of the roof. The living area is surrounded by terraces and gardens. The 3 meter thick bunker roof was dug into to make room for the planting of trees and for a pool that is used for bathing and to reflect sunlight into the living area. Movable metal screens along the perimeter of the roof give privacy to the outdoor living spaces.
The apartment is laid out as an open plan with the living spaces flowing through the entire area. The art collection connects into the living area in the centre of the plan in a large gallery space. The living spaces in the apartment are characterised by simple reinforced concrete walls and a concrete ceiling. The plan is based on a grid of 1.875 meters and has a ceiling height of 3.75 meters.
Part of the open plan living area are besides the gallery, an open plan kitchen set up higher on a platform, a living and dining area with an open fire place suspended from the ceiling, a work area and a more private living area from which the bedrooms and bathrooms can be reached. Roof lights give additional daylight for internal spaces such as the gallery space and the guest bathroom.
The woodwork for the cupboards, doors and wall panels are made of smoked oak. The slabs for the lacutrine lime stone floor have been cut across the veining. The same stone is used for the washbasin, bathtub and the work surface in the kitchen but cut with the veining. It has a rough surface when used as wall lining in the shower rooms and chipping of the same material will be used in the garden areas.
The project was developed by Realarchitektur in cooperation with the client and an interdisciplinary team. An important programmatic theme has been living with art, new and old, and connecting these. The design process has been situational. In the Bunker new is mainly created by subtraction. Floors and walls have been taken out giving way to overlapping spaces that join the floors vertically. On top of the building structures are being added that relate closely to the existing ones in the Bunker. As well as spatial structures also materials have been reinterpreted. It has been our aim to work with situations as found in the existing bunker.
The livings spaces were completed in 2007, the collection was opened in 2008. The Bunker project is nominated for the Contractworld award and the Mies van der Rohe prize, it was Awarded with the German architectural prize Architekturpreis Beton 2008, nominated for the nordic Architectural prize Forum AID. The Project has been exhibited at the Bienale in Venice 2006, in the Weissenhof Gallerie 2007 and at the Intercity Berlin-Prag in 2008.
Photos: Hanns Joosten (10, 11, 13, 14, 20), Noshe (1, 5, 6, 7, 8, 9, 12, 15, 16, 17, 18, 19, 20), Baubild – Stephan Falk (2, 3, 4), Kajofoto – Karl Johaentges (21, 22)
Christian Boros and Karen Lohmann
Jens Casper, Petra Petersson, Andrew Strickland
Wolfgang List, Bernadette Krejs, Karin Maria Derix
Project Partners, Quantity Surveyors and tender:
Frank Hüpperling und Stephan Vieweger
Ingenieurbüro Herbert Fink
mib, märkische ingenieurbau gmbh, Wriezen
Steel and facades:
HTM Metallbau, Berlin
BBT Betonbohr- und Sägetechnik GmbH, Berlin
Berghäuser und Sohn
Asta Fliesen & Naturstein GmbH, Polanz
Rentschler und Riedesser, (consultation) und Bast Heizungsbau (plans and installation)
Project start 2003, on site 2004, completion 2007, opening Sammlung Boros 2008
ca. 16.500 m³ exhisting building
ca. 750 m³ Concrete was removed
ca. 2.500 m² area for the Art collection
ca. 2.500 m³ house
ca. 450 m² living area