Relationship between height and footprint area with cost for tunnel form high-rise buildings

The goal of this study is to determine the relationship between height and building unit cost (i.e., cost per gross floor area) for high-rise buildings and to identify the effect of footprint area of buildings to this relationship. previous studies on height and unit cost relation of high-rise buildings are limited and mostly do not discuss the details of the height-cost relationship with respect to elemental costs or major work costs. in this study the relation between height and unit cost were analyzed by examining the cost data of 65 high-rise (between 25 m and 142 m) residential buildings that were built with tunnel form between the years 2006 and 2013 in istanbul. the results demonstrate that the total cost of the building, elemental costs (e.g., substructure), and some major work (e.g., concrete) change with height. similar to the prior studies in the literature, the cost-height relationship identified in this study has a u-shaped curve; however, the bottom-out point is around 65 m. besides determining the height-cost relationship, another contribution of this study is investigation of the effect of footprint area on the cost-height relationship. for buildings with small and large footprint areas, cost-height relationship is u-shaped, while for buildings with medium footprint areas unit cost increases as the height of the building increases. results also show that the unit costs of buildings with medium-size floorprint areas are lower than that of the buildings of the same height but with larger footprint areas. the findings of the study can be used by academicians, architects-engineers and practitioners to understand the cost-height-footprint area relationship and to make more cost-effective decisions about the height and footprint area of a building, especially in areas where height restrictions do not exist.