Purpose As an underlying entity in the discourses of privatisation of space, urban security and fear, boundary walls are considered as an impediment to the publicness of public spaces. But, the inevitability and potential of their physical attributes and functions is indicative of the lack of systemic knowledge on how to approach boundary walls, so that they contribute positively to the quality of urban spaces. The paper aims to discuss these issues. Design/methodology/approach Since boundary walls are constitutive of physical attributes that are embedded with multiple functions, the contribution of physical boundaries is premised on the interaction between objective and subjective measurements, explored in positive and ambiguous space types. In this study, the quality of physical boundaries is measured by an index and the perceived functions of the physical attributes of boundary walls are measured by a questionnaire survey. Findings This study found that positive and ambiguous space types not only affect the quality of physical boundaries but also the perceived functions of the physical attributes of boundary walls. Further, social and visual functions of boundary walls play a significant role in contributing positively to the quality of urban spaces. Originality/value By exploring the relation between quality of physical boundaries and their perceived functions, this study extends the meta-understanding of the role of boundary walls.