California housing crisis: Inside the push to ramp up the ‘backdoor revolution’

California lawmakers and housing advocates are intensifying efforts to expand what some are calling a "backdoor revolution" in addressing the state's housing crisis through lot splitting initiatives, particularly under Senate Bill 9.

The legislation, which took effect in 2022, allows homeowners to split their single-family residential lots into two separate parcels and build up to four housing units total, effectively bypassing traditional zoning restrictions that have limited housing density in many communities.

The push represents a significant shift in California's approach to increasing housing supply, as SB 9 enables property owners to create additional housing units without going through lengthy and often contentious local approval processes.

Homeowners can either split their lots and sell one parcel for development or retain both parcels while adding housing units themselves.

For property developers, this creates new opportunities to acquire split lots in established neighborhoods where land was previously unavailable for multifamily development.

Housing experts view lot splitting as a crucial tool for addressing California's shortage of affordable and middle-income housing, particularly as traditional large-scale development projects face increasing costs and regulatory hurdles.

The "backdoor revolution" terminology reflects how these smaller-scale housing additions can cumulatively create substantial increases in housing stock while working within existing neighborhood frameworks, potentially transforming single-family neighborhoods into more diverse housing communities over time.