Old Bricks, New Roots: Seismic Retrofit and Adaptive Reuse of Unreinforced Masonry Buildings with Mass Timber and Urban Infill

Abstract

Unreinforced masonry (URM) buildings are an integral part of the urban fabric of West Coast cities due to their historic significance, material richness, and contribution to human-scaled streetscapes. Despite their cultural and architectural value, these structures are highly vulnerable to seismic activity and are increasingly threatened by demolition within rapidly densifying urban environments. Conventional seismic retrofit systems rely heavily on carbon-intensive steel and concrete interventions that are environmentally costly and architecturally intrusive. This thesis proposes a novel mass timber retrofit system that simultaneously seismically reinforces and adaptively transforms an existing URM building in Seattle for long-term use. Urban analysis conducted in the Seattle neighborhood of Belltown identified a recurring relationship between URM buildings and adjacent vacant lots, revealing opportunities for new structural and spatial interventions. The project leverages this condition by introducing a mass timber structure on an adjacent site that provides lateral reinforcement while incorporating new vertical circulation and programmatic expansion for the existing building. The design draws from the tectonic language and geometries of historic regional timber structures, positioning mass timber not only as a sustainable structural material but also as a continuation of the Pacific Northwest’s timber heritage. By integrating contemporary mass timber systems with historic masonry construction, the thesis reframes a seismic retrofit as both a preservation strategy and an architectural opportunity capable of extending the cultural, spatial, and urban relevance of existing URM buildings.