Restoration of the south curtain wall of the Wartburg Castle in Eisenach, Germany

The Wartburg Castle in Eisenach is one of the best preserved medieval castles in Germany and dates back to the year 1067. Over the centuries, it was extended with buildings from the Romanesque and Gothic period and building components from the 19th century to form an expansive castle complex, which - last but not least - became famous as Martin Luther's sanctuary.

The south curtain wall is about 800 years old and consists of large, compact natural stones whose mortar joints were highly weathered. The masonry was very damp, as water was able to penetrate especially into the bond area between the natural stones and the mortar and accumulated in the fissured interior area. Severe moisture penetration into the whole of the masonry and damage due to alternating frost and thawing were the result. To solve this problem permanently, the joints near the surface and the bond area between the natural stones and the mortar needed to be sealed in such a way that all water ingress would be prevented.

To do so, a mortar was required for the new jointing which was adapted to the masonry type and fulfilled the requirements on the preservation of the ancient monuments as regards reversibility. Extensive preliminary examinations proved the suitability of the 1-comp. bituminous acrylate dispersion WEBAC_® 5611; the material's tensile strengtth is approx. 0.3 N/mm² and is thus considerably higher than that of the existing mortar.

For the restoration of the curtain wall the joint mortar close to the surface was first removed down to approx. 3-5 cm. The joints were then sealed by applying WEBAC_® 5611 and jointed anew with mortar afterwards.

These measures helped to seal the bond area between the natural stones and the morar such that surface water can no longer penetrate. The differing shrinkage and expansion behavior of the materials (caused for example by seasonal temperature fluctuations) is easily compensated by WEBAC_® 5611.

Once again, WEBAC_® 5611, which has been tried and tested for many years, demonstrated its suitability for use in the preservation of ancient monuments, and the WEBAC team is pleased to have been able to contribute to the preservation of the Wartburg Castle world heritage site.