Humboldthain Flak Tower
Conversion, extension and long-term plans for an Air Raid Bunker in Berlin for the running of a Food Co-operative.
The Humboldthain Flak Tower was built in World War II to hold anti-aircraft guns and provide shelter for 15,000 civilians. Originally consisting of four towers, allied attempts to destroy the building at the end of the war left two towers standing. The remains are predominantly hidden by a rubble mountain of 1.5 million cubic meters of debris from the war bombings. The tower is situated in a residential park area just north of central Berlin in close proximity to major rail and road intersections. With its constant temperature and humidity throughout the year, this space is ideal for the storage and presentation of fresh produce. The proposal is dedicated to a food co-operative as storage, point of sale and for community-based work and activities. With Berlin’s very high rate of unemployment, the co-operative programme will also provide the creation of part-time jobs .
Inside the bunker, the spaces will be created by what remains of the structure with additions only where it serves the needs of the programme. The only subtraction from the form will be selected removals of post-1945 in-fills with the exception of internal windows to allow the kitchen space to function. Elevators will be replaced in the shafts and new additions to the stairs and extra walkways will be added. These are to have a continuous language of ionised steel to complement, but yet differentiate them from the original structure. A steel structure for a canopy to accommodate a café is to be added to one tower and a multi-use function room to the other. The steel from the height-reduction of the existing perimeter fence is used to build the canopy and internal space; both of these structures are derived from the existing geometric configuration inside the bunker.
In 1940, the Nazis ordered the construction of six anti-aircraft, or ‘Flak’ towers, to defend Berlin from enemy aircraft. Of these six, only three were built. After the war the British destroyed the other two and the Russians partially demolished Humbolthain. Half of the tower at Humbolthain still stands, but is predominantly hidden by a rubble mountain which was shifted towards the towers in an attempt to cover them up. They couldn’t be covered completely due to the proximity to the train lines to the north. The inside of the bunker was also filled with rubble. One thousand trees were planted on the man-made hill and the bunker was sealed after the fatal accidents of intrepid explorers. 3.5m high fences along the edge of the towers and the platform below were introduced to reduce accidents and suicide attempts. Since 2003, the group Berliner-Unterwelten e.V. have owned the flak tower and run tours. Most days, a local rock-climbing group can be seen ascending the north-western façade.
The proposal creates an environment that nurtures an awareness of growing and consuming food sustainably and reliably. A community-run organisation would be housed and provide local people with healthy, fresh food that is produced within the vicinity of the Brandenburg area.
The food will be brought into the bunker as close to ground level as possible. It will then take a path from the storage, through the shop display and out at the top, either from the sale of raw goods or by use in the kitchen and finally the café. (fig.1). Waste at every level of the food’s journey is collected at points near the elevators on each floor and then taken down the building and out again through the delivery route. (fig.1) Raw and cooked food waste is composted on site and UHT glass sterilisers will enable the direct reuse of glass without the usual recycling process. An outdoor café and function room are structures added to the roof top. The steel structures predominantly coming from the 2.5m long fencing off-cuts. The kitchen is situated directly below the café; the food is transported to café level through a 600mm existing hole by a small dumb-waiter. When fully cleared of rubble an estimated 3000m2 of floor space becomes available. A longer-term project of the food co-operative would be a seed collection bank in the basement. This will safeguard quality seeds for future generations.
Although the running of a food co-operative requires membership to function, there is no fee and anyone can join. The part-ownership of this type of institution cultivates a sense of belonging and pride. Everybody commits 3 hours a month to the organisation and benefits from reduced rates on the food. One challenge for a food co-operative is to allow new-comers to experience what it is about. The prescribed walkway through the building serves to break this barrier between the co-operative and the public. (fig. 2) Visitors and tourists may also use it to experience the character of the bunker and to learn about its history. It is designed not to interfere with the general every-day running of the food co-operative. Only the staircases are shared with regular shoppers. In contrast, the cross-over routes one takes around the shop as a member, and the various points to pack or sort, create more chance meetings and interaction between shoppers. (fig. 3)
Minimal heating and cooling is required in most areas of the bunker. The whole bunker remains below 10oc all year round. (fig. 4) Overcoats are offered at the entrance. Offices for the co-op’s organisation and rental studio spaces are an isolated unit and heated locally. Food is stored and presented in temperatures and humidity levels best suited to their preservation. Dry storage for ‘grain’ type produce requires rooms with controlled humidity. Similar to the heated rooms, they are isolated and locally controlled. Cold working conditions means that short shifts suit the members and the scheme well. Water-saving devices are implemented through rainwater collection tanks from the roof deck. Purification tanks complement the mains water supply to the building.
The food co-operative already has a vested interest in sustainability by sourcing only local produce. Deliveries to the building have travelled a maximum of 100km from anywhere in the Brandenburg region. Regular events and courses are held in the demonstration garden to inform the public of growing and consuming food.
Materials and Conservation:
When all rubble from inside is cleared, approximately one fifth of the original flak tower is usable again. The varied surfaces of the concrete walls, ceilings and floors and other traces of the building's history will remain visible. Little repair work is necessary to preserve the outer façade. Along the length of the interior of the building the floor falls away at about a 50% decline due to demolition attempts. This destructed space that was built to withstand extreme forces can be experienced on gridded walkways over the inclined rubble (see photo-montage 2). The inner surfaces are sealed to food-safety standards. The floors are re-covered with concrete to minimise dust settling on the food. Wet areas for washing vegetables and crates are tiled for easy-maintenance and the reduction of moisture in less well ventilated areas such as the delivery level (see photo-montage 3).The removal of window in-fills are made only where necessary. No incisions are made in the 3m thick reinforced concrete roof slab due to extremely high energy and cost issues. Only the 600mm hole to the top deck will be reopened for the kitchen-to-café connection. Steel tube profiles from the perimeter fence (20mm and 50mm in diameter) are reused for the structure of the canopy and function room.
A Berlin Community Food Project
A new food cooperative in Berlin called’ Dickes Bee’ committed to providing food in an ethical, sustainable and environmental way would reside in the proposed building. At present they are an informal, community project intent on thorough product research, building personal relationships with farmers, environmental conservation, animal-rights and a 100% working membership.
Members are invited to regular trips to farms who supply the co-operative. It is a great way for urban dwellers to connect with the countryside and to become aware of how food is produced. ‘Dickes Bee’ have a personal relationship with every person who grows, raises and processes the food ordered. They are careful to source only from farmers who have open door policies.
Recently, having joined my local food co-operative, Dickes Bee, I learnt there are many more benefits than solely wholesome food. Many activities involving sport, current affairs, music and culture are planned by the members. After partaking in one of the co-operative’s activities (a beginner’s swing dance lesson), I was pleasantly surprised at everyone’s willingness to contribute their ideas and knowledge to the project proposal.
This gave me a grounding to better understand the needs of the food co-operative. A great evening of discussion was followed by numerous changes, alterations and additions in the usage of certain areas. The long-term plan for the seed collection was also drawn up as an on-going project that the team would work on.