Low-cost housing development in South African's post-Apartheid era is overwhelming; dealing with a fragmented and segregated urban inheritance and a housing demand which exceeds delivery capacity. In response to insufficient delivery, the destitute have turned to informal backyard renting. Backyard dwellings can accommodate a multitude of tenants in one or two roomed wood, or corrugated iron structures, constructed by tenants in the backyards of homes provided by government housing schemes. The backyard rental sector is widely described as unsustainable; however, this paper argues that the sector may, in principle, be one of the most sustainable aspects of South Africa's housing development culture. This paper analyses the benefits and disadvantages related to the continued growth of the informal backyard sector and explores the value of the sector as a supporter of Smart Growth through infill development, increased densities and as a countermeasure to urban sprawl. In an attempt to evaluate the sustainability of backyard living, the living conditions and additional pressures placed on infrastructure and transport networks, as a result of backyard rentals, are examined. The main research question to answer is: Is Smart Growth supported by the informal backyard rental sector and what sustainability pressures are exerted as a result thereof? The research for this paper includes surveys conducted in the case study area of Oudtshoorn in South Africa's Western Cape Province, interviews with relevant stakeholders and an evaluation of existing literature. The conclusions drawn may provide evidence for the need to regulate and develop the backyard rental sector in order to improve the lives of backyarders and the efficiency of the South African city.