Lime mortars in conservation -- traditional materials and craft for the future

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Eva Backlund

Plaster made from lime is environment-friendly, repairable and sustainable. Despite this, lime plaster on historic buildings has been replaced in modern times by plaster containing Portland cement – which has caused severe damage to historic buildings. Experts, researchers, craftsmen, manufacturers and authorities from throughout the Nordic region are now assembling for the 10:th Jubilee Conference on lime and lime mortar, with the aim of promoting historic buildings, as well as new build, access to traditional building materials. When the Nordic Building Limes Forum was formed in 1999 it was as a reaction against the harsh treatment of historic buildings all over the Nordic region, where original lime plasters were replaced with hard, cementitious mortars. Today Kalmar Castle, the ruins of Borgholm Castle and Läckö Castle bear the marks of this harsh treatment. The castles, which are a part of Sweden's national cultural heritage, are now being repaired using traditional, locally produced lime mortar, says Ewa Sandström Malinowski, PhD, Architect SAR/MSA, at the Department of Conservation, University of Gothenburg.

Läckö is a unique project

Läckö Castle, dating from the Middle Ages and rebuilt and extended in the 17th century, was replastered with cementitious mortar in the 1960s. The plaster on the castle's 10,000 square metre façade today shows serious signs of decay due to damp, frost and salts. The National Property Board, which owns and manages the castle, consequently instituted an extensive new restoration of the castle's exterior. This provided the opportunity for a Nordic research team consisting of conservationists/architects, chemists, geologists and building-archaeologists to develop and "re-create" the traditional lime plaster through a unique research project. The research is co-ordinated by the University of Gothenburg.

Nordic conference

One of the goals of the Läckö project has been to develop methods for the conservation and repair of architectural heritage – but also to pave the way for lime plaster and traditional craftsmanship to be used on historic buildings.

The Nordic Building Limes Forum, a network that brings together craftsmen, researchers, producers, officials, architects, administrators and contractors from throughout the Nordic region, is holding a conference at Kalmar Castle on 1-2 October.

Representatives from related European lime networks – from the UK, Ireland and Italy – participate in the conference. The conference will present current research and restoration projects such as the ongoing works at Kalmar, Borgholm and Läckö Castles, where local materials, produced on a small scale, are applied.

"If we are to keep the traditional crafts alive we must also adapt them to modern building techniques. Lime and lime mortar, which are sustainable and eco-friendly materials, can be readily used even in new build," says Ewa Sandström Malinowski, researcher at the Department of Conservation, University of Gothenburg, and responsible for planning the conference.

Source: University of Gothenburg