The Kreuzbau (also Klassenkreuz) is a building type for school buildings in Hamburg. Between 1957 and 1963, Kreuzbau buildings were erected there at a good 60 locations of state schools. They have four wings on a cruciform ground plan, from which the name is derived. The Kreuzbau building has three floors and a flat roof. Each floor has four classrooms and associated small group rooms, which means that the Kreuzbau building can accommodate twelve school classes. The classrooms are directly accessed by a central staircase - without a corridor and in the way of Schustertyp. The design for the Kreuzbau building came from the Hamburg building director Paul Seitz. The main advantage of this type of building was its rapid assembly; from today's perspective, its disadvantage is its lack of thermal insulation. More than 80% of the Kreuzbau buildings erected in Hamburg are still standing and mostly serve elementary schools as classrooms.
History
Antecedents After the end of World War II, almost half of Hamburg's former 463 school buildings were no longer usable: 21% of the schools were destroyed and 26% were so badly damaged that they could hardly be used. From 1945 to 1947, the number of students in Hamburg doubled from 95,000 to 186,000. The reasons for this increase were the return of families from the 1943 evacuation after the "Feuersturm," including students returning from the "Kinderlandverschickung." The settlement of 1944–50 flight and expulsion of Germans and refugees from the Soviet occupation zone had a reinforcing effect. Until 1948, school construction was limited to makeshift repairs of damage and the use of shacks and other temporary facilities. The shortage of space could only be met by "shift teaching."Reiner Lehberger: Schule in der Nachkriegszeit. Auszug aus Lehberger, de Lorent: Schulen in Hamburg. Brunswiker & Reuter, Hamburg 2012,
This situation generated considerable public pressure, since parents' gainful employment was severely hampered by staggered shift teaching of several children. In Hamburg's state politics, the shortage of space in schools was, along with the housing shortage, the irritant par excellence and contributed to the SPD's loss of its majority in the 1953 Hamburg elections, even though top candidate Max Brauer promised the completion of one new school per month in the election program "A flourishing Hamburg."Christel Oldenburg: Tradition und Modernität – die Hamburger SPD von 1950–1966. Lit, Berlin 2009, , pp. 216 f. The winner of the 1953 elections was the bourgeois Hamburg Block, which used the issue of the lack of school buildings to stop the school reform pushed by the SPD. But that did not change the urgent task of multiplying the pace of school construction. At the same time, however, the city's resources were limited - there were enough other expensive tasks in housing construction and industrial settlement.
In 1952, Paul Seitz was appointed First Director of Construction and Head of the Structural Engineering Office in Hamburg, and thus also Deputy to the Senior Director of Construction at the Hamburg Building Authority, Werner Hebebrand. Seitz held these posts until 1963, when he left Hamburg for a professorship at the Berlin University of the Arts.Boris Meyn: Der Architekt und Städteplaner Paul Seitz. Hamburg 1996, S. 83. Seitz designed mainly schools, university buildings and other public buildings during his ten-year tenure. For schools, he relied entirely on serial designs that were used according to the modular principle. In doing so, he pursued two concepts: the "Green School" and the "wachsenden Schule."Boris Meyn: Der Architekt und Städteplaner Paul Seitz. Hamburg 1996, S. 9 ff.
The Green School was intended to realize ideas of the new education movement of a return to nature by placing smaller school buildings with a maximum of two stories on generously sized school grounds in the green, ideally with direct access to the garden from the classroom. This type of construction deliberately stood out from the imposing "school barracks" of the Wilhelminism Period and was intended to appear transparent and light. The dimensions of these buildings were to have a human scale, a deliberate contrast to the old school buildings in which a "whole generation was drilled in racial ideological and militaristic values." It is true that school construction was not the focus of Nazi architecture, since hardly any new schools were planned and completed between 1933 and 1945. However, the new school buildings were also intended to express a turning away from the secondary virtues that had made the Nazi state and world war possible.Peter Krieger: "Wirtschaftswunderlicher Wiederaufbau-Wettbewerb" : Architektur und Städtebau der 1950er Jahre in Hamburg. Universität Hamburg, Hamburg 1996, urn:nbn:de:gbv:18-136, S. 205–207 (Hochschulschrift). Das Zitat dort auf p. 205.
The "wachsenden Schule" was to be available quickly and then grow with the needs of the school. Initially, this concept also called for school buildings to be easily relocatable, and was accompanied by the abandonment of costly foundations and basements.Michael Baltzer, Hartmut Gerbsch: Paul Seitz: Fliegende Bauten. In: Westwerk und HafenCity Universität (Hrsg.): Katalog zur Ausstellung in der Reihe "Stadt-Schnitt", Teil 1, Hamburg 2012, pp. 22–37. (Online) The first series of pavilion schools was built in Hamburg according to this concept; a much-noted prototype for this type of construction at the time is the listed Mendelssohnstraße school in Bahrenfeld. The serial construction developed in the process was the pavilion type A, made of lightweight materials by Polensky & Zöllner. By 1961, 459 new classrooms of this type had been erected.Boris Meyn: Die Entwicklungsgeschichte des Hamburger Schulbaus. Hamburg 1998, pp. 257–259.
Design phase The design task for Seitz and his working group in the structural engineering department was clear: How could new school construction in Hamburg be drastically accelerated despite a labour shortage of skilled workers and budget constraints without abandoning the ideals of the Green School"? What could a series design look like that would also work on smaller or denser school sites? And how would this serial design have to be designed in order to represent all functions of a school as a nucleus of a "wachsenden Schule" already in the first construction phase? The answer to these questions was the Kreuzbau building.
The labour shortage of skilled workers in the construction industry was a major obstacle to accelerating the school building program. Conventional buildings needed skilled masons, foremen, scaffolders, and roofers. Public school construction competed for these skilled workers with residential construction and the private sector. The use of precast concrete reduced the need for such skilled workers on the job site, while the quick 15-day erection time allowed the erection crew to move on, after which the build-out continued. The standardized school construction reduced the need for skilled workers in the shell construction phase to specially trained assemblers - the construction time was already reduced to one fifth by the "Pavilion A" assembly system.Boris Meyn: Die Entwicklungsgeschichte des Hamburger Schulbaus. Hamburg 1998, pp. 256–257.
The pavilion schools were cheap and quick to build, but they usually had only one or at most two stories, and a correspondingly high land consumption. This required a plot size of at least 24,000 m2 for an Volksschule with the usual class frequency of the time. This was still possible in the planned new development areas in the expansion areas of Hamburg (e.g. Rahlstedt and Bramfeld), but in densification areas such as Wilhelmsburg and Wandsbek or to replace war-damaged school buildings near the inner city, as in Horn and Hamm, these plot sizes were not available. In addition, it became apparent that the influx and birth rates in the new development areas were higher than expected, so that the already designed schools had to accommodate higher numbers of students. A classroom building of more than two stories with a good ratio of usable to circulation space was essential to achieve the necessary space efficiency.
In response to the design task, Seitz developed the Kreuzbau building starting in 1955. The three-story arrangement made better use of the land than a single-story pavilion. In addition, the direct access to the classrooms from the staircase resulted in a very favorable ratio of 80% usable space to 20% circulation space. However, the lowest grades of a school were still to be housed in pavilions accessible at ground level. The design relied heavily on precast concrete elements and placed great emphasis on rapid erectability. The small heating cellar with oil-fired heating made it possible to start school operations immediately, even in winter, regardless of progress in further construction phases.
In 1955/56, a pre-series type of the Klassenkreuz was built for the school at St. Catherine's Church. This prototype, in contrast to the series production, had four floors, because the plot of land at the Katharinenkirchhof was only 7,000 m2 and thus lacked space for the erection of further school buildings. The school at the St. Catherine's Church was listed as a historical monument,Verzeichnis der erkannten Denkmäler nach § 7a Hamburgisches Denkmalschutzgesetz, Auszug Bezirk Hamburg-Mitte, Stand: 25 June 2007, p. 99. (Online) but was nevertheless demolished in 2011 in favor of the newly to be built "St. Catherine's Quarter".Ansichtssache. In: Quartier, , Nr. 07 (September–November 2009) The school is located at the Katharinenkirchhof.
Construction phase
From now on, the Klassenkreuz was to serve as the centerpiece and first construction phase of the "wachsenden Schule". After it was erected, classes could begin immediately in the Kreuzbau building, while other school buildings were added all around. Ideally, the following sequence was typical:Das Hamburger Klassenkreuz. In: Das Werk, , Band 50 (1963), Heft 6, pp. 234–236.
First construction phase: Klassenkreuz Second construction phase: classrooms with differentiation rooms in pavilions Third construction phase: administration rooms, janitor's apartment, common room / break hall Fourth phase of construction: classrooms, gymnasium (side hall), smaller gymnasium, auditorium
The space available in the Klassenkreuz was in accordance with the specifications of the Room and Furnishing Program for Hamburg Schools of 1958. The production of the prefabricated parts for the Kreuzbau buildings was entrusted to the "Arbeitsgemeinschaft Kreuzschulen," which consisted of Polensky & Zöllner and Paul Thiele AG.
The prototype at the St. Catherine's Church was accepted on August 9, 1957.Bürgerschaft der Freien und Hansestadt Hamburg (Hrsg.): Sicherheitsmängel an "Kreuzbauten" im Brandfall, Schriftliche Kleine Anfrage der Abgeordneten Sybill Buitrón Lübcke (CDU) 8 October 1997 und Antwort des Senats 17 October 1997. Drucksache 16/5, 16. Wahlperiode. Four more approvals of Kreuzbau buildings followed before the end of August 1957. Based on the experience of the first series of ten, the construction time for a Kreuzbau building was half a year, half of a "normal" school building. The planned cost would be 670,000 marks per Kreuzbau building.Klassenkreuze nach Maß. In: Hamburger Abendblatt, ISSN 0949-4618, 10. Jahrgang, Nr. 198 (27 August 1957), p. 3. (Digitalisat) At the end of August 1957, school inspector Dressel announced that the new construction method would eliminate the school space shortage in Hamburg in four to five years.