At this place the City Wall of Visby collapsed on the 24th of February 2012. Approximately 90 m2 of the outer masonry leaf fell and left a big hole in the wall. The top was balancing on the ruined wall, the inner core being visible. The collapsed wall was very unstable, at its thinnest parts it was not more than 25 cm wide.
Why did the wall collapse? There were several reasons; a ground level that is 2½ meters higher on the inside of the wall, high levels of moisture within the wall due to repointing with cement mortar which leads to deterioration, poor bonding between masonry leafs and several freezing cycles in the weeks before the collapse.
The Swedish National Heritage Board is the property manager of the City Wall, which is owned by Region Gotland. It was decided that the reconstruction should be carried out as a research project in collaboration with Uppsala University, Tyréns, Byggnadshyttan pà Gotland and Gotlands Museum. The possibility to increase knowledge of Medieval masonry and conservation methods in parallel with the reconstruction of the wall was seen as being very valuable.
In order to create a safe working environment and to be able to rebuild the wall in a stable manner, it was necessary to take down the top and the part of the collapsed wall that was still standing. A temporary steel structure was built around the damaged part and then the wall was fixed between it using granulated foam glass. Thereafter the wall was dismantled stone bv stone.
On 9th of May 2014 the first stone was laid and during the summer the new part of the wall was rebuilt. The medieval materials and structural principles using limestone, local clay and lime mortar were used. The old walls on the sides of the collapsed part were fixed with tie rods with visible anchor plates. In October 2014 the last stone on the wall was laid. Finally the new wall was crowned by a thin top in concrete.
As a recognition for the well performed work the project was awarded by DBW's Annual Building Conservation Award in 2016.
