Unreinforced stone masonry buildings in New Zealand: Inventory and material characterisation

The high seismic vulnerability of unreinforced stone masonry (URM) buildings was once again demonstrated in the recent Canterbury earthquakes (2010-2011). The shortage of knowledge about New Zealand historic URM buildings, and about techniques for their conservation, led to numerous losses, both in terms of lives and architectural heritage. Almost all URM buildings in New Zealand were constructed between 1860 and 1910, typically in regions where natural stone (in particular basalt, schist and limestone) was sourced from local quarries, fields and rivers. There are estimated to be approximately 688 URM buildings in New Zealand, with most being a potential earthquake risk. As a first step, an inventory of the URM buildings of New Zealand was compiled, listing location, construction details and architectural configuration. A further development was the inspection of representative case study buildings, where architectural characteristics and extracted material samples were obtained. Compressive tests and petrographical analyses were undertaken on natural stone specimens, while compressive strength and mineralogical composition were determined for mortar samples. The aim of the study reported herein was to acquire a thorough understanding of the mechanical and physical properties of these URM buildings in order to assess seismic vulnerability factors and potential seismic improvement solutions.