en.Wedoany.com Reported - Germany – The retaining walls on both sides of the old synagogue in the Hohenlimburg district of Hagen are being demolished and rebuilt by Spesa Spezialbau und Sanierung GmbH due to structural tilting and partial collapse, with restoration of the historic masonry in accordance with heritage protection requirements. The project, commissioned by Wirtschaftsbetrieb Hagen AöR (WBH), aims to permanently eliminate structural safety hazards.
Built in 1870, the synagogue is located on a narrow hillside terrace and currently serves as a museum and event venue. The two retaining walls support slopes with gradients of up to 40 degrees and adjacent embankments. Structural inspections revealed that one retaining wall had tilted, while another section had collapsed. Previously, large bulk bags were used as temporary supports, but they severely restricted the work area. Material assessments determined that due to severe deterioration, restoration could only be achieved through complete demolition and reconstruction.
Site manager Sebastian Otto stated that the bulk bags provide necessary structural support and can only be removed gradually, adding logistical challenges to the confined site. Since the two retaining walls were not built as load-bearing or heavy walls, but only to stabilize the surface rock behind them, demolition is relatively straightforward. The existing damage is primarily attributed to weathering and root pressure from the upper rock layers.
Construction first involves carefully removing the existing natural stone, which will be fixed, temporarily stored, and prepared for reinstallation in accordance with heritage protection requirements. Due to limited space, storage poses a logistical challenge, but detailed mapping of each stone is not required. After demolition, a shotcrete shell is applied using drilling rigs and excavators to stabilize the slope. Over an area of approximately 150 square meters, 75 tons of shotcrete will be applied, with an additional 110 anchor bolts used for reinforcement. Only after the load-bearing slope stabilization system is completed will the retaining wall be rebuilt using the original historic stones. Existing brick masonry on site will no longer be used; all reconstruction will be done solely with natural stone. Missing stones will be replaced with locally comparable natural stone to preserve the historic appearance.
In the gap between the shotcrete shell and the natural stone masonry, single-grain concrete will be filled in layers. Otto noted that this method allows precise control of the pressure exerted by the fresh concrete, and the new natural stone wall will not bear the load of the slope, only supporting its own weight and the pressure from the drainage layer. Work began in February and is expected to be completed by July 2026. Through this restoration, Spesa contributes to preserving this culturally significant site and improving the visitor environment.
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