SB 10 creates a process by which the city council can increase the density in residential areas up to 10 units per lot in a jobs-rich area, or on land near public transit, or in areas of urban infill. The resolution can specify the height limit and it can bypass the typical environmental review process when rezoning.
The Terner Center at UC Berkeley suggests SB 9 could increase the housing stock in California by about 700,000 over the next decade. As building additional units is voluntary, the number will depend on landowners being willing to reconfigure their properties. Cities are required to approve these proposals if they meet the specified size requirements and design standards.