This study concerns both the utilization and deterioration of natural building stone employed in the construction of Cologne cathedral. Built during the middle ages at the same time as the Cologne cathedral, the cathedrals at Xanten and Altenberg reveal the use of comparative natural building stone not only at the time of their original construction but also during later building and restoration/conservation work. The following text considers correlations between these cathedrals and examines the stone used and the building histories, i.e. construction, reconstruction and repair work, for all three cathedrals.
Figure 2.1 South elevation of the Cologne cathedral
Cologne cathedral (Fig. 2.1) represents the archdiocese of Cologne. Its present day form stems from 1248 following the demolition and burning of parts of the original cathedral.
Already in 1164 there was a pressing need for the building of a new cathedral due to the donation of the relics of the Holy Three Kings combined with an increase to the number of pilgrims (Schock-Werner et al. 2011). The new building work was commenced in 1248 under the authority of the first master cathedral builder and mason "Meister Gerhard" (Wolff 2005), the building´s principal and the financier comprised the cathedral chapter (Beuckers 2005).
The laying of the foundation stone by Archbishop Konrad von Hochstaden took place on the fifteenth of August of that year.
Figure 2.2 Xanten cathedral from the South East (Schubert, Dombauhütte Xanten).
Xanten cathedral (Fig. 2.2), which in 1263 succeeded various Carolingian and Ottoman-Roman predecessors, is the gothic ecclesiastical building of the canonical foundations in Xanten that prevailed in the eighth century (Bader 1964). Having been begun by "Meister Jakobus" and with contributions from 1396 to circa 1406 by a "Meister Gerhard" of Cologne (Hilger 1995), the cathedral was finally completed after a three hundred year construction period in the sixteenth century (Bader 1949). The new gothic style, employed in the building of the Cologne cathedral, encountered in many other churches and cathedrals at that time with their five delineated spaces and column figures in the main choir, acted as a model for the building of the Xanten cathedral (Bader 1949). The gothic construction integrated the grand west front, which had only been built fifty years previously in the Staufer era. Though the architectural arrangements of Xanten cathedral´s southern portal exhibit a late gothic interpretation of Cologne cathedral´s "Petersportal", the chancel area in particular
church was sourced through the assets of the chapter of canon and from the sale of letters of indulgence (Bader 1964). The laying of the foundation stone by Friedrich von Hochstaden, the provost of the Xanten canonical establishment, occurred in 1263.
Figure 2.3 Altenberg cathedral, as seen from the East. (©Heidemarie Wolf, Odenthal)
Begun a mere eleven years after the commencement of building work to the cathedral in Cologne, Altenberg cathedral (Fig. 2.3) is a Cistercian church that had financial contributions from the von Berg counts. Undoubtedly, this was a situation very agreeable for both parties.
Through participation in the expansion of the cloister the noble sponsor could consolidate a territorial and political sphere of influence and profit from an increase in agronomic authority.
Also the cloister embodies a suitable site for the interment for the representative of the sovereign powers. In turn the cloister enjoys protection as well as the security provided by the rich proceeds resulting from generous donations and profits generated through use of the cloister. The Altenberg cathedral´s master builder, having been employed at the Cologne building site, must have been extremely familiar with Cologne cathedral´s construction. The blueprints of the Cologne cathedral chancel as a basis for the chancel area at Altenberg were improved by reference to older differing calculations from Amiens and Beauvais.
(Lepsky and Nußbaum 2005; Heydasch-Lehmann et al. 2008)
The proximity in time between the start of the specific building projects of the three houses of god is remarkable. They reflect the enormous building activity of the twelfth and thirteenth centuries in the Rhine-Maas-region (Beukers 2005). Autonomous building projects were the result of the individual architectural arrangements, the different specific used formats of
natural stone ashlars at the three sites and the distinct building organizations as well as the specific standalone building consortiums comprising the Cathedral Chapter, Chapter of canon or Noble sponsorship (Graue et al. 2013b).
Drachenfels trachyte was the singular building material employed at all three sites during the construction phase of the Middle Ages. This natural building stone had been popular since Roman times due to its balanced degree of strength, which would expect a good workability verses and a relative adequate resistance to weathering (Berres 1996; Scheuren 2004).
Figure 2.4 Lithological map of the south elevation of the Cologne cathedral (Windscheid (2004) after Wolff and Luckat 1973)
The construction of the Cologne cathedral began in 1248. The medieval part of the cathedral was built of Drachenfels trachyte from the nearby quarry at the Siebengebirge. The construction was halted at the beginning of the sixteenth century and then recommenced during the nineteenth at which time Drachenfels trachyte was no longer available. At the beginning of the nineteenth century efforts to obtain Drachenfels trachyte reached a conclusion in 1829 with the expropriation proceedings by the Prussian king Friedrich Wilhelm the third. As a reason was quoted the danger posed from uncontrolled rockslides. A much more important inducement would have been the desire to protect the middle age ruins at the Drachenfels, and the victory monument from 1814 commemorating the end of Napoleon´s reign, and also because Drachenfels had by this time become a tourist attraction of
international renown. This prohibition of further stone mining can be seen as one of the first measures of monument and landscape protection (Berres 1996 ; Scheuren 2004).
In the 1820ies, when first repair works started and the construction of the cathedral resumed, local stone available from the Siebengebirge was the primary choice as a replacement material. Initial renovations were conducted using latite obtained from the “Stenzelberg” and a few supplementary materials from the quarries of the Siebengebirge. After a short period it was apparent, that the Stenzelberg latite was a very time intensive and therefore cost
graywacke, several sandstone, basalt lava, tuff, Stenzelberg latite, Krensheim Muschelkalk Restoration works
1995 – 2006
Krensheim Muschelkalk
In the middle of the 19th century the second construction phase used sandstone from
“Schlaitdorf” in southern Germany. Later with the establishment of the railway connection linking Cologne and Minden, it was possible to transport the “Obernkirchen” sandstone from Lower Saxony. The so called third construction phase, comprising restoration works, started in 1903 and lasted until WWII, during which time the “Krensheim Muschelkalk” was the
typical stone utilized. In the 1950’s, the decay resistant basalt lava from “Londorf” was used.
At the present time, the trachyte from “Montemerlo” in Italy is being used to replace the deteriorated Drachenfels trachyte and a sandstone from “Bozanov” in the Czech Republic for the weathered Schlaitdorf sandstone (Fig. 2.4;Tab. 2.1) (Scheuren 2004; Schumacher 2004).