BALKSTEN KRISTIN1, THELIN CARL2

1 Ph D Associate Professor, Uppsala University, Konstvetenskapliga institutionen, kristin.balksten@konstvet.uu.se

2 Ph D, Tyréns, Historic Buildings, carl.thelin@tyrens.se

The City Wall in Visby was built in two periods in 13th and 14th century. The first wall was made as a lower three-leaf wall with two shells built of lime stone and fat lime mortar and a soft and porous rubble core of lime stone and clay mortar. The second wall was built higher on top of the old one. It was mostly built as a solid wall in lime stone and lime mortar. Due to its construction and form, a major part of the force is carried by the outer shell of the wall. As restorations have been made during 20th century the joints of lime mortar has been partly repointed with strong cement mortar, followed by leached lime inside from the mortar in the wall. In February 2012 a part of the wall collapsed and fell down as the outer shell of the masonry collapsed. This paper presents an analysis of the wall structure and its materials as well as the increased risk of damage due to the restorations of the 20th century.

Keywords: city wall, lime mortar, clay mortar, three-leaf wall, rubble core, masonry structure, deterioration