This paper presents a series of speculative growth scenarios in Melbourne that test how medium-density infill models can respond to short- and long-term housing needs. The scenarios employ a multi-scalar, design-led research method that simultaneously examines:

• The physical outcomes that can be achieved at a built-form level; 
• Strategic planning directions at suburb and regional levels;  
• Population and housing distributions at suburb, region and city scales.  

Three comparative scenarios explore the type and volume of housing that middle ring suburbs will need to accommodate, relative to other development activity across the city: Business as Usual (65% infill 35% fringe); Best practice (70% infill 30% fringe); and Ambitious (75% infill 25% fringe).