Unreinforced Masonry Precincts in New Zealand: History, Heritage, and Seismic Retrofit

Abstract

New Zealand’s built heritage tradition is one of persistence and innovation, that continues to evolve in response to social and environmental conditions. Extensive damage caused by natural disasters such as the Canterbury earthquake sequence (2010-2011) focused public sentiment on an overlooked historic construction typology: unreinforced masonry (URM) buildings. The findings of the Canterbury Earthquakes Royal Commission (2012) highlighted a high proportion of deaths that occurred in public places, as a result of collapsed nineteenth- and twentieth-century URM buildings during the earthquakes. Throughout New Zealand, many such buildings were built in clusters and therefore survive as historic areas or precincts. Arising from the need to address public urban safety in conjunction with privileging historic building fabric, this thesis employs architectural heritage conservation as a framework for examining New Zealand’s history, heritage, and seismic retrofit of URM precincts. Heritage conservation through seismic retrofit demands analysis of architectural and structural seismic design principles. The thesis examines the application of contemporary conservation theory through selected case studies that document and analyse the history, significance, and seismic retrofit initiatives for URM precincts in New Zealand. The principal research question is: how can an understanding of architectural history and heritage conservation inform the selection of seismic retrofit and structural upgrading solutions to privilege the historic fabric of URM building precincts in New Zealand? The theoretical basis and practical challenges informing the analysis are captured by a series of sub-questions, including: To what extent does international architectural heritage conservation theory address pre- and post-disaster seismic and structural upgrade of historic URM building precincts? How may a multidisciplinary precinct-scale approach to seismic retrofitting historic buildings help to achieve greater urban safety? This thesis shows that New Zealand cities and towns feature an evolving, living, architectural heritage tradition of URM construction, built between 1880 and 1930. Examining national and international discourse reveals a shift in focus of conservation principles and practice, from individual buildings to precinct. The documented histories of change and adaptation suggest that the local URM precincts should be treated as examples of a functioning, built heritage when considering pre- and post-earthquake interventions and future role.