Complex scaffolding for renovating the roof of the Marschiertor in Aachen
The employees of the Aachen-based scaffolding company Creutz literally hit the roof of the Marschiertor, once the south gate of the outer city wall around Aachen. It numbers among the largest still remaining town gates in Western Europe. Building work on it began around 1257 and it was probably completely shortly after 1300. Greatly damaged during the 2nd World War through bombing, the gate was initially only provisionally restored. The roof in its present form only dates back to 1951.
“Innumerable leaks in the shingle roof that could no longer withstand the harsh weather influences from storm and rain made a comprehensive renovation necessary”, according to Engelbert Chaumet, the project leader from the town of Aachen. Therefore, to protect and preserve the roof structure, elaborate renovation work already began in April 2017. The scaffolding needed for the roofers to work from at a height of up to 50 m was to span the entire gate. The medium-sized company Creutz with over 100 years’ experience in scaffolding took on the assignment supported by the engineering firm Specht in Schalksmühle, which was responsible for the statical calculations for the individual scaffolding sections.
In this respect the scaffolding of the characteristic pitched roof represented one of the biggest challenges. According to the project leader Chaumet, the scaffolding could not be assembled directly on the roof since it was not able to take-up such heavy loads. Therefore, to scaffold the ridge turret, load-bearing towers out of RUX-SUPER-100 façade material were initially erected, on which lattice girder bridges out of 700 mm high steel lattice girders could be laid. These were then additionally affixed over the ridge of the pitched roof to the left and right of the ridge turret. The scaffold for the work on the roof turret was fitted onto these bridges – similarly, with SUPER façade scaffolding from the Hagen-based manufacturer scafom-rux.
The scaffolding of the roof slopes was effected by means of a special steel tube structure. Short 450 steel lattice girders were fitted over the segments of the roof structure from the façade scaffolding and then supported on the ceiling of the structure in the upper floor by means of scaffold tubes. These supporting tubes penetrated the roof structure. The roof scaffolding out of scaffold tubes and couplers was constructed on the lattice girders protruding inwards. The standards for this scaffolding were fitted at an inclination to match the respective roof slope. Pressure anchors out of pivotable base jacks with a load-distributing wooden brace were pressed against the roof surfaces at every scaffold node.
During work on the roof areas, the individual pressure anchors could be loosened to enable work up to a wind force of 5. At the end of the shift or in the event of wind forces in excess of 5 on the Beaufort scale, all anchors needed to be firmly tightened down again. In view of the complexity of these technical solutions, the circular scaffolding and anchorage on the two narrow sides of the gate almost seemed like child’s play. Sheeting and wooden planking, that could be adapted to the shape of the building, was used to secure the site against any falling items. Additionally, projecting platforms enhanced safety for pedestrians and traffic on the street running near to the Marschiertor. “It was particularly the nearness to the street that made assembly so difficult and we were only allowed to put anchors at specific points in the joints of the wall”, reports managing director Wolfgang Creutz. The imposing scaffolding with a size of 70 metres and a height of 22 floors shows that every challenge can be overcome. Some 140 tonnes of scafom-rux scaffolding was installed and fitted in 40 days.
All those involved assume that the restoration work will be completed by the winter and that the Marschiertor will once again shine like new punctually for Christmas.