V - The magazine of the VOLLMER Group - 2018

and his expert team. All stones were examined, touched and their condi- tion was critically eyed. Result: Of the 12,800 sandstones 2,800 must be completely restored and another 1,800 in the attached Münsterbauhütte (cathedral workshop). Every stone is marked on a three metre long cata- logue of measures and has a corre- sponding coloured processing note. Extreme maintenance – the dimensions at Ulm Minster are massive. What maintenance means in rela- tion to the Ulm Minster becomes clear when one takes a look into the small hall directly beside the church surrounded by scaffolding. In the fully completed for 125 years. Strictly speaking, it is about roughly a quarter of the tower whose structure partially originates from the Middle Ages. The project started under the management of the current Minster builder Michael Hilbert in 2015. This work alone will keep him and his 19-man team busy for an estimated 10 years. Stony work on area the size of a football pitch. A total of just under 6,000 square metres are being worked. This corre- sponds to roughly the size of a football pitch. At which point stones have to be replaced or restored was discussed from 2011 to 2015 in a patchwork never-ending task by Michael Hilbert Ulm Minster Practised religion – maintenance work Minster builder Michael Hilbert never runs out of work. The preservation of the Ulm Minster built in 1377 is a never-ending story, the Gothic stone giant is a perpetual construction site. A current mam- moth project is now the restoration of the main tower, which has been VIEW INTO THE MÜNSTER- BAUHÜTTE (CATHEDRAL WORKSHOP). WORK ON THE TALLEST CHURCH STEEPLE IN THE WORLD (161.53 M). so-called Münsterbauhütte (cathedral workshop), which is also home to a joinery and forge, one can watch the stonemasons at their painstaking meticulous work. A separate resto- ration concept is developed here for every individual stone. The largest stone processed to date weighed 1.8 tonnes. It was removed from a height of 70 metres, transported down with the cargo lift and brought from there to the workshop. Its restoration took a good 400 hours. Between 30 and 40 hours are spent working on smaller stones. The installation at the dizzying height requires another 30 to 40 hours, technical expertise and good nerves. The enemies of sandstone: weather conditions, people and sandstone itself. But what is required so that a sand- stone can be restored to its former glory? Within the framework of the restoration work many blocks are cleaned, cleared of moss and lichens and desalted. A binding agent is also often injected before they are further processed with diverse stone masonry. There are various reasons why the stones become damaged. On the one hand due to their age: Some stones are up to 500 years old. Cracks develop over long periods of time in the constant alternation of frost and heat, through which water can now penetrate. Another reason is mankind and the environmental impacts they cause. Acid rain and air pollution by the consumption of oil and coal for heating have meant that on the sur- face lime has been transformed into water-soluble plaster, which makes the stone fragile. Last but not least, the stones themselves cause problems. Because different types of sandstones have different degrees of hardness and different properties with regard to water absorption. In this way virtually every stone damages its slightly differ- ent neighbour. Enough work for the next century. The work on the main tower should take up to 2025. Other maintenance projects are also professionally managed at the same time. Interior restorations, fire protection projects, gate transformations: Everything is held together by modern building monitoring. Current project in 2018: Mould threatens the Gothic choir stalls with their superb handcrafted wood- carvings. They are in desperate need of cleaning. Perfectly clear: The chal- lenges don't stop the Minster builder Michael Hilbert. The dimensions of the church are so big that you constantly have to interfere here or there. That's just the way it is! And this also won't change in the next centuries. The biggest stone processed to date weighed 1.8 tonnes. 30 31 PERSPECTIVES