Renovation | Stone walls Petersberg Citadel Erfurt

The old, high fortress walls look as imposing as ever thanks to the joint renovation with maxit mur 950 HS - with a grain size of 0 - 4 mm and matched in colour to the existing structure. Thanks to the dry spraying method used and the subsequent surface treatment, the fortress walls shine in new "old" splendour after completion of the work.

The Petersberg rises in the centre of Erfurt and is home to the Petersberg Citadel, one of the largest baroque city fortresses in Central Europe. As part of the BUGA (federal horticulture show) Erfurt 2021, the infrastructure of the elevation was extensively renovated.

In addition to Preuße & Rätsch from Weimar, construction companies such as Hopp from Weimar and SEB Baugesellschaft from Kromsdorf were commissioned to repair the defence walls. The mighty walls enclose the Petersberg in two rows and, according to their bastions, were divided into the construction sections Bastion Johann, Bastion Martin, Lauentor and Bastion Kilian. Large surface areas, deep joints, structural strengthening and the most perfect possible adaptation to the existing natural stone masonry - these were the special challenges and demands of the renovation.

The walls are quarry stone walls with different dimensions of joints in width and depth. In order to grout the old walls, which are about 5 km long in total, evenly in terms of colour and surface structure, maxit mur 950 HS with highly sulphate-resistant cement as a binding agent was chosen. A specifically coordinated formulation was also developed for this object. With the product maxit mur 950 HS recipe Petersberg, the wishes of monument preservation were explicitly addressed.

The quarry stone masonry was grouted by machine using the dry spraying method and thus with perfect craftsmanship. Compared to manual grouting, mechanical grouting proves to be more cost-effective and of higher quality, especially for large areas, and is therefore particularly interesting in the case of historic city walls or e.g. castle complexes. After dry spraying, the surfaces were exposed again with a blasting material so that, on the one hand, the natural stone was freed from the mortar and, on the other hand, a rough, visually even surface was created in the joint area.

Preuße & Rätsch GmbH, Weimar | Hopp Company, Weimar | SEB Baugesellschaft mbH, Kromsdorf

Time period:
2017 - 2021

Application thickness:
Deep grouting, jointing


  • maxit mur 950 HS, 0 - 4 mm, coloured

Project location