After decades of cessation in council house building and depleting stock numbers, local authorities have recently been given the means to start building again to meet the UK housing shortage. Low density council owned estates, in particular post-war mid to high rise estates, present an obvious opportunity to deliver intensification through infill development. Infill development, however, should benefit existing residents by addressing major problems, such as poor-quality open spaces and the tenuous relationship with the street. This study proposes a tool-kit to guide infill development on post-war, mid to high-rise estates in an attempt to find out how infill development can improve open spaces and the relationship that estates have with the streets. The tool-kit incorporates principles brought to light in a literature review of council estate regeneration theories and infill development case studies on post-war, mid to high rise estates. A design response on the Home Park Estate utilising the tool-kit is used to evaluate the tool-kit, leading to a conclusion that infill development implemented in accordance with the tool-kit would produce higher quality, more useful open spaces and strengthen the relationships that estates have with the wider street to produce safer and more cohesive streets. Further research is needed to determine resident’s aspirations for infill development and to determine the financial viability of infill.