The Alsterschwimmhalle, which has become a unique element for the entire city of Hamburg, is particularly exemplified by the careful and precise restoration of the highly acclaimed roof by gmp Architekten, which is a balance between conservation, functional redesign and meeting changing user demands, thereby ensuring the long-term functionality and operation of the pool and its surroundings.
The 50-metre pool, the 10-metre diving tower and the so-called “fitness cube” on the east side have been preserved with very few modifications. However, the old tiered seating at the poolside was dismantled to make room for a new, separate diving pool. In addition, the extension building to the north was demolished and a new one- or two-storey building was built, housing a new series of pools, a changing room area, a gym and saunas, increasing the existing water surface by a quarter and reconstructing just over half of the total surface area.
Alsterschwimmhalle by gmp Architekten. Photograph by Marcus Bredt.
Project description by gmp Architekten
The ceremonial reopening of the Alsterschwimmhalle will take place on November 24, 2023. As one of Europe’s largest shell buildings, the indoor swimming pool, designed by architects Horst Niessen, Rolf Störmer, Walter Neuhäusser, and the engineer Jörg Schlaich, is an outstanding example of Hamburg’s post-war architecture. At the time, the concrete shell roof, which consists of two hyperbolic paraboloid shells carried by three supports, reminded Hamburg’s citizens of the Sydney Opera House – and since then, has been lovingly nicknamed “Schwimmoper” (“Swimming Opera”). The spectacular shell roof, the enormous interior with the 50-meter pool, and the facade construction were retained. At the same time, the sports facilities were comprehensively redesigned for the first time and supplemented with contemporary additions.
Originally, the Alsterschwimmhalle was constructed as a competition venue but over time it became a leisure pool for the general public. Despite its 400,000 visitors in 2014, for financial reasons closure of the pool, demolition, and construction of a new modern building was under discussion. In cooperation with schlaich bergermann partner (sbp), gmp developed a feasibility study that became the basis for the decision to retain and refurbish the building. A key element in this decision was the fact that the spectacular roof had been given listed status. Covering a floor area of 4,500 square meters, the roof – which is only 8 centimeters thick and held up by three diagonal support struts - soars to a height of 24 meters at its tips. Two of the three support points are linked via a tie beam beneath the swimming pool. With spans of up to 96 meters, the roof is still one of the largest of its kind in the world.
"The Alsterschwimmhalle is a true highlight of technical architecture, which has become a unique feature for the whole city of Hamburg, especially thanks to its striking roof construction. I am very pleased with the smooth and successful restoration, in which all the planning and coordination processes with Bäderland and gmp Architects worked in an exemplary manner and this wonderful architectural monument from 1973 can continue to be used to its full potential by the people of Hamburg."
Dr. Anna Joss, Head of the Denkmalschutzamt Hamburg.
The big challenge regarding structural safety related to the fact that parts of the old pool had to be demolished and rebuilt without modifying the existing roof or disturbing it during construction work. This meant that the tie beam between the foundations could not be touched and was constantly monitored during construction work. Having completed the refurbishment, the roof is protected against damage from rising chlorine, high humidity, and high temperatures using a new cathodic corrosion protection system (CP).
The 50-meter pool, the 10-meter diving tower, and the so-called “fitness cube” on the east side have been retained with very few modifications. However, the old, now barely used tiered seating beside the pool was dismantled to provide space for a new, separate diving pool. Furthermore, the extension building to the north was demolished and replaced by a new one- to two-story building. This accommodates a new 25-meter swimming pool, a training pool, a barrier-free entrance area, as well as changing rooms, fitness facilities, and saunas. Overall, the existing water surface area has been increased by a quarter; just over half of the total internal area has been rebuilt. A new forecourt has been created in front of the main entrance. Vehicular access is now via Sechslingspforte, which means that the neighboring residential quarter to the east, at Ifflandstrasse, benefits from traffic calming. The newly created pedestrian route from east to west connects the residential quarter with the inner city.
The original aluminum trussed columns of the glass facade have been retained. gmp, sbp, and Implenia Fassadentechnik also developed a new building-code-compliant telescopic piston support system that forms a flexible connection between facade and roof; this makes it possible to compensate for oscillating movement of the roof shell. The surfaces of the retained building components were restored to recreate the original face concrete appearance, using elaborate restoration techniques, or returned to the original former color scheme. Construction elements such as the historic acoustic tiles were restored and reinstalled. The architectural identity of the indoor pool facility was retained whilst striking a balance between preservation, functional redesign, and meeting changes in user demand, thus ensuring the pool’s long-term functionality and operation.
