Self build: Global South Fernando Murillo University of Buenos Aires Abstract. While the industrialised North regulates urban development through strict legal frameworks, urbanisation in the South happens mostly through self build practises out of any formal regulatory framework by. This has significant impact on people daily life conditions and urban sustainability at long term. The article explores formal and informal cases, representing regions of the global south: The Gaza Strip (Autonomous Palestinian Territories), Khartoum (Sudan), Kigali (Rwanda), Rio de Janeiro (Brazil) and Buenos Aires (Argentina). The cases shed light on self build rationale, serving as driving force for individual survival and according to their particular context, also long term community development strategies. Such context can be analyzed from a social angle: How communities historically develp self help regulatory mechanisms to share and optimize the use of scarce resources. Geographical variables play also a major role: Topography, natural ecosystems, densities and location into the urban fabric shape certainly the sustainability of human settlements. Finally, the particular legal framework applied to regulate self build phenomena, understanding or neglecting all factors mentioned earlier, promoting or preventing informality, and community self regulatory mechanisms providing social safety networks for survival of the poor. Finally, it is analysed self build contribution to progressive development of sustainable design and urbanisation trends: Spontaneous popular higher densities, mixed land uses, multi-storey energy efficient buildings, recycled materials, harmonising formal frameworks and community self regulations. Keywords: Self build global south, formal and informal settlements, legal frameworks, community self-regulatory mechanisms, urban poor, sustainability. Glossary of terms Self-build: Activity normally perform by low income groups to satisfy their housing needs through permanent or transitory materials, applying techniques and skills adapted to their income and resources availability. The activitymay involve individual or community efforts, in the second case could involve also the construction of basic urban infrastructures. Creativeness to optimize scarce resources results remarkable. Global south: Those low industrialized countries, typically dependent of exporting natural raw materials, where poverty and environmental problems are major threats. In general they are lowly industrialized and with high percentage of low income population, reflected in their housing conditions.