Suburbanised cities share a common dilemma: how to transition to more densely populated and socially connected urban systems while retaining low-rise character, avoiding gentrification, and opening neighbourhoods to more diverse housing choices. Bluefield Housing offers a new land definition and co-located infill model addressing these concerns, through describing and deploying the types of ad-hoc modifications that have been undertaken in the suburbs for decades. Extending green-, brown-, and greyfield definitions, it provides a necessary middle ground between the 'do nothing' attitude of suburban preservation and the 'do everything' approach of knock-down-rebuild regeneration.An adjunct to 'missing middle' and subdivision densification models, with a focus on co-locating homes on small lots, Bluefield Housing presents a unified design approach to suburban infill: retrofitting original houses, retaining and enhancing landscape and urban tree canopies, and delivering additional homes as low-rise additions and backyard homes suited to the increasingly complex make-up of our households.Extensively illustrated by the author with engaging architectural design studies, Damian Madigan describes how existing quirks of suburban housing can prompt new forms of infill, explains why a new suburban densification model is not only necessary but can be made desirable for varied stakeholders, and charts a path towards the types of statutory and market triggers required to make bluefield housing achievable.