<p>South African urban form remains in dire need of spatial transformation. This need arises from the spatially engrained nature of race-based segregation and inequality that was established under apartheid, and which endures to some extent in the present urban form. This research explored the impact of residential expansion on spatial transformation by investigating whether residential expansion reproduces or disrupts past patterns of racial diversity in Gauteng, South Africa. It analysed residential land use data and population estimates that were aggregated to hexagon shapes in the study area. The micro-scale analysis reveals important patterns that are not visible at other scales or through segregation indices. Calculations show that between 1990 and 2020, roughly 905 km² of predominantly residential areas were added to the Gauteng residential footprint. However, in Gauteng as a whole, this residential expansion does not relate to a higher racial diversity. There remains a distinct spatial separation between new residential areas, with low and high racial diversity. A few public and private residential developments have had some positive impact, but none of these have necessarily made an impact in the direction of desired spatial transformation. Urban planning has not altered the availability and distribution of affordable housing to contribute to increased levels of race and class diversity. These findings imply that urban planning has not maximised the potential benefit of new residential development for spatial transformation.</p>