Evaluating the Effects of Open Shelters on Limestone Deterioration at Archaeological Sites in Different Climatic Locations

Open shelters have been proposed as suitable preservation strategies for a variety of heritage sites. However, no concerted attempt has yet been made to analyze their performance in a range of climatic conditions. This study aims to quantify limestone deterioration outside and inside the shelters at two archaeological sites, Hagar Qim (Malta) and the Bishop’s Palace (England), to obtain information on their impact. A simple methodology based on exposure trials and non-destructive tests was used. Globigerina limestone blocks were exposed at both sites from July 2013 to July 2014. Changes in appearance, weight, hardness, color, and moisture content of the blocks in addition to temperature and the likelihood of NaCl crystallization and freeze-thaw events were assessed over the year. This research shows that while deterioration rate is reduced as microclimatic conditions are moderated, open shelters do not completely prevent limestone deterioration at either site, especially in relation to salt weathering.