The Grossmarkthalle is to house a visitors’ centre, a staff restaurant, a cafeteria and conference rooms. These areas will be integrated into the hall as a separate house-in-house system. The original 1920s hall floor and its sub-structure are not strong enough to support these new building elements, thus necessitating a new structural framework. There will also be a new, waterproof basement that will house the archives and technical rooms.
In the summer of 2010 diggers took down the reinforced concrete ceiling and reinforced mushroom columns. These works had no impact on the structure of the Grossmarkthalle, as the diagonal columns that support the roof shells rest on separate footings that extend down to the basement.
The installation of the foundation piles for the new building elements and the construction of approximately 3,500 drilled metres of concrete underpinning for the existing column footings were completed in 2010.
The purpose of the entrance building is to create a functional and visual link between the Grossmarkthalle and the double office tower. It will intersect with the Grossmarkthalle to form a clearly identifiable entrance from the north side of the site on Sonnemannstrasse. It will also house the press conference area.
In order to enable the construction of the entrance building, three segments of roof were pulled down in August 2010, upon agreement with the historic preservation authorities. The three concrete shells that were removed were those that were damaged during the Second World War air raids and subsequently reconstructed in the 1950s.
They were removed by diggers according to a carefully devised plan: first, the facade was taken down, leaving the structural framework of the roof shells. Then the shells themselves were removed, and finally, the structural framework, which consisted of reinforced concrete supports, was also pulled down. The diggers followed this plan meticulously, so as not to damage original parts of the building.
The restoration of the Grossmarkthalle, which was built between 1926 and 1928 according to a design by Professor Martin Elsaesser, is an important aspect of the construction works. The basic appearance of the building will be retained, with its facades and surfaces being restored in line with the preservation order. In 2010 approximately 7,000 m of horizontal joints and 32,500 transversal joints in the wing buildings were removed and reinstalled. In addition, approximately 14,000 defects in the concrete were repaired.
The concrete core of the entrance building, which has already emerged out of the gap in the hall, now shows the location of the entrance building and its alignment towards Sonnemannstrasse.
The new basement and ground floor, as well as the first few floors of the “house-in-house” building elements, are now in place, and the wide set of stairs, which will lead up to the conference area, already gives a first impression of the dimensions and proportions of the new internal buildings in relation to the hall.
The roof shells were constructed using the Torkret process, which was state-of-the-art at the time and one of the reasons why the Grossmarkthalle became a listed building in 1972. The shells are being restored, and, contrary to initial fears, their quality has turned out to be amazingly good. The outer surface of bituminous roofing felt and styrofoam film is being removed so that a new layer of insulation can be applied, while the inner layer of concrete is being restored.
Since the spring of 2010 the brick facade of the eastern wing building has been being repaired. This has involved removing the mortar from all the joints and replacing it. The joint profile of the brick facade constitutes one of the Grossmarkthalle’s special features: according to the design of Martin Elsaesser, who was Director of Town Planning for the City of Frankfurt am Main at the time, the width of the transversal joints was to be considerably wider than that of the vertical settlement joints, i.e. two and a half centimetres compared with only one centimetre. The idea was to accentuate the horizontality of the brick courses. This artistic accentuation of the horizontality was further underlined through the colouring of the joints, with the horizontal joints being filled with a pale mortar and the vertical settlement joints with a dark mortar. The aim of the careful restoration of the joints is to replicate this original feature of the facade.