Nairobi’s urban processes today are largely impacted by global and postcolonial forces. Its inherited planning frameworks keep contributing to the self-sustaining systems of socio-economic inequality and exclusion of the urban poor in a capitalist society. At the same time, its urban planning reflects postcolonial processes, characterised by the global dominance of Western knowledge and the assumption of its universal applicability, as well as the pursuit of the ‘modern’ urban imaginary. Derived within this context, the standard mainstream upgrading and (re)development practices to address informal areas are unsustainable: showing ineffective (participatory) processes, providing solutions unfit to local circumstances and needs, and mainly indicate our limited epistemological understandings. This project responses to this trend, by approaching the informal settlement as spatial manifestation of implicit knowledge by the subaltern (‘subaltern urbanism’ (Roy, 2009;2011)(Varley, 2013)) in order to explore alternative development perspectives. It approaches local knowledge as the implicit knowledge that arranges space and governance. The research analyses Mathare Valley, Nairobi, and uncovers its spatial, social, and economic structures, including the organisation of local governance. The aim of the project is to explore how local knowledge and a community-based approach can provide a base for a strategic framework to guide sustainable development in Mathare Valley. As a final outcome, the proposal of an integrative strategic framework combines spatial and non-spatial interventions, introducing a local co-operative organisation that forms the heart of the community’s collective process of empowerment. Accompanying the strategy is the community action plan, meant as inspiration for the community on how to instigate such a process. This thesis’ relevance derives from its appreciation of the depth of informal settlements, its contribution to a contextualised understanding of sustainable development, and the promotion of a broadening of urban concepts and understandings to discover new insights on more effective and sustainable solutions within the context of development of informal urban areas.