New Research Project: Historical Town Hall and Granus Tower in Aachen
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Even today, the historical Town Hall together with the Granus Tower to the north and the Aachen Cathedral to the south of the Katschhof still bear witness of Charlemagne?s Palace. In addition to the archeologically proven remains of the Carolingian site and despite many reshapings and much destruction, these two buildings keep important evidence of the imperial palace as well as Carolingian and medieval original substance in their foundations and walls.
While research and science have been able to wring many insights on the building history from the Marienkirche (St. Mary?s Church), today?s Cathedral, neither a complete documentation nor systematic building research has been done with reference to the King?s Hall on whose foundations the gothic Town Hall was erected in the 14th century. Therefore, first intensive building documentation and research was begun in the Granus Tower, the former ?turris regalis? of the Carolingian palace, in the Spring of 2007. Within the seminar ?Building Research as the Basis of Preserving Measures for Historical Monuments? the research fellows Judith Ley and Marc Wietheger and several students measured the building systematically, documented it with illustrations and photos and described it scientifically during several one-week documentation campaigns on-site.
Apart from the practical teaching of different examination methods and techniques for historic building substance within the student course in Preservation of Historical Monuments, the production of exact architectural as-built drawings and building condition analyses are also meant to accommodate the requirements of preservation as well as upcoming maintainance measures.
Still, the main goal of the work, which was supported by the Aachen Office for Preservation of Historical Monuments from the beginning, should be to define the different building phases and thus the original shape and purpose of the building by analysing the on-site findings as well as other historical sources. By way of tachymetric CAD supported online measuring, photogrammetric images of stoneface surfaces, 3D laser scanning and manual measurements of details, deformation-compatible as-built drawings were produced. In this way, all the main and intermediate storeys were captured in detailed ground plans as well as six vertical sections within one consistent measurement reference (3D traverse). On this basis, building joints, used materials, damage patterns and particuliarities in the building material treatment were exactly mapped so that, afterwards, the complex inner space structure could be analysed. The analysis of the Tower?s level structure, the direction, accessability and illumination of its rooms and staircases as well as the integration into resp. connection to the former King?s Hall and to the whole palace is of special importance in this.
In the short-term, the well-advanced work on the Granus Tower should be expanded to the historic Town Hall: When looking more closely into the various building joints, the seemingly informal coexistance of the two building parts presents itself as a complex, inter-dependent space structure, whose analysis may well yield conclusions as to the original architectural concept.
The intermediate results and aims of the ongoing building research are discussed in different panels with colleagues and those involved in the project and also introduced into the recently founded study group Palace Research in Aachen.