Design determinants of core efficiency in tall timber buildings: a typological analysis

This study investigates core efficiency in tall timber buildings by analyzing how vertical core configurations influence usable floor area. As timber gains traction globally as a sustainable material for high-rise construction, understanding the spatial implications of core design becomes increasingly relevant for both architectural performance and economic feasibility. The primary aim of this research is to evaluate the relationship between core-to-GFA (gross floor area) ratios and five key architectural variables: core design, building form, function, structural system, and material composition. Unlike prior typological studies that examined service cores primarily in relation to energy, overall space-efficiency, or narrative reviews, this paper isolates the core-to-GFA metric and links it—quantitatively—to core placement, form, function, structure, and material in tall timber only. This research is grounded in a comparative analysis of 50 tall timber cases, employing descriptive statistics, typological classification, and graphical evaluation methods. Key findings indicate that: (1) Central core configurations generally show lower average ratios (11.36%) than peripheral (13.3%) and external (17.3%) cores. (2) Residential functions were associated with relatively lower ratios, and while prismatic geometries supported straightforward core layouts, free and tapered forms recorded even lower average ratios in this dataset. (3) Timber-only structures recorded comparatively lower ratios (9.8%), suggesting higher efficiency than hybrid systems such as timber–concrete and timber–steel composites. These observations may offer practical insights for different stakeholders. Architects could optimize floor efficiency through centralized planning; engineers might consider structural strategies that accommodate lean cores; developers can benefit from improved net-to-gross ratios; and policymakers may take these patterns into account in performance-based code development for sustainable high-rise timber construction.