Foldness: A Measurement Index for Building Facade Richness in Old Residential Areas and Evaluation of Urban Spatial Vitality

Abstract

This paper proposes the Foldness indicator system for quantifying the building façade richness in old residential areas, including Foldness Index (F), Average Depth (AD), and Coefficient of Variation of Depth (). These three parameters respectively characterize the frequency of facade contour changes, the amplitude of setbacks and protrusions, and the regularity of the form. Taking Wuhan’s Wucai Zhengxiang as a case study, this research combines laser distance measurements with time-segmented behavioural observations to explore the relationship between this indicator system and community vitality. The findings indicate that the three indices effectively differentiate the morphological characteristics of traditional brick-wood buildings (orderly richness), mixed-type buildings (disorderly complexity), and modern renovated buildings (flattening). The index of F shows significant correlation with spatial vitality; together with , it explains nearly 70% of the variance in vitality. Foldness affects spatial vitality through three pathways: visual attraction, support for edge spaces, and positive perceptions generated by moderate complexity. Sheltered nodes (e.g., under canopies) often become all-weather social gathering spots. This research suggests that Foldness can serve as an effective tool for urban spatial quality evaluation and management towards more inclusive and sustainable urban neighbourhood rehabilitation.

Keywords: Foldness, Building Facade, Old Residential Areas, Spatial Vitality, Urban Renewal

DOI: 10.54941/ahfe1007291