Informal settlement is a form of incremental urban design and planning that seems set to remain a primary mode of urban development in cities of the global South. Yet, we know very little about how incremental urbanism works. In this paper, we suggest a typology of increments as a conceptual lens for understanding the emergence of informal settlement morphologies. We consider the ways residents extend and renovate buildings at micro-spatial scales and identify typical increments of ‘extend’, ‘attach’, ‘replace’, ‘divide’, ‘connect’ and ‘infill’. We also explore the informal rights and codes that govern the ways in which some increments encroach on public space – ‘rights of way’, ‘air-rights’ and ‘the right to light and ventilation’. We engage with the paradox that while every increment is a form of upgrading, informal settlements often produce slum conditions. We suggest that the most effective knowledge base for slum upgrading practices lies in a better understanding of informal settlement as a mode of spatial production.

非正式住区是渐进式城市设计和规划的一种形式，似乎仍将是全球南方城市的城市发展的主要模式。但是，我们对渐进式城市化的运作方式知之甚少。在本文中，我们建议采用增量类型学作为概念镜头，以了解非正式沉降形态的出现。我们考虑居民在微观空间尺度上扩展和翻新建筑物的方式，并确定“扩展”，“附着”，“替换”，“划分”，“连接”和“填充”的典型增量。我们还探讨了非正式的权利和法规，这些法规和法规规范了某些增量侵犯公共空间的方式-“通行权”，“空气权”和“采光权和通风权”。我们有一个悖论，即每次增加都是一种升级形式，非正式的定居点经常产生贫民窟的条件。我们建议，贫民窟改造做法最有效的知识基础在于更好地了解非正式居住作为一种空间生产​​方式。